5.4 context與global的應(yīng)用

5.4.1 使用context實(shí)現(xiàn)計(jì)數(shù)器

　　在之前的流中，我們總是在執(zhí)行函數(shù)節(jié)點(diǎn)時(shí)新建一個(gè)變量。函數(shù)節(jié)點(diǎn)執(zhí)行完畢以后，這個(gè)變量的值就會(huì)丟失，沒(méi)有辦法保存。如果需要保存一個(gè)變量的值該如何操作？
　　可以借助context對(duì)象。它可以理解為上下文，或者語(yǔ)境，用于保存內(nèi)存中的數(shù)據(jù)，這個(gè)數(shù)據(jù)可以持續(xù)保存到下一個(gè)消息到來(lái)。Context可用于保存索引，計(jì)數(shù)或者消息中的數(shù)據(jù)。
　　拖入inject節(jié)點(diǎn)與debug節(jié)點(diǎn)。拖入一個(gè)函數(shù)節(jié)點(diǎn)，進(jìn)行如下設(shè)置：

　　完成以后連線并部署。多次點(diǎn)擊inject節(jié)點(diǎn)的輸入按鈕，并在調(diào)試窗口觀察現(xiàn)象。

　　發(fā)現(xiàn)調(diào)試窗口中的數(shù)據(jù)在遞增

　　接下來(lái)結(jié)合現(xiàn)象分析代碼：

var count = context.get('count')||0; //如果count不存在就初始化為0，已存在則獲取count的值 count += 1; context.set('count',count); //執(zhí)行完+1操作以后保存count的值 msg.payload = count; return msg;

　　我們可以查到Context的一些API（應(yīng)用程序接口）如下

context.get(..) : 獲取一個(gè)節(jié)點(diǎn)范圍內(nèi)的上下文屬性 context.set(..) : 設(shè)置一個(gè)節(jié)點(diǎn)范圍內(nèi)的上下文屬性 context.keys(..) : 返回所有節(jié)點(diǎn)范圍上下文屬性鍵的列表 context.flow : 同 flow context.global : 同lobal

　　每次的輸入都不變，count每次都+1,最后輸出遞增的數(shù)，說(shuō)明count記錄了上一次輸入的值。執(zhí)行Context.get以后，就可以獲取到之前保存的值。
　　執(zhí)行context.set以后，就能把處理過(guò)后的值保存下來(lái)。保存到哪里？’count’,帶單引號(hào)的count里。接下來(lái)用流程圖來(lái)表示邏輯。注意，帶單引號(hào)的’count’與變量count不一樣

　　流程保存在這里

[{"id":"1e2326a1.bc3da9","type":"inject","z":"dfef6fbd.55491","name":"","topic":"","payload":"1","payloadType":"num","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":690,"y":160,"wires":[["ecb5fce2.ce1dc"]]},{"id":"7e2fd11b.d4b4","type":"debug","z":"dfef6fbd.55491","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","x":1100,"y":160,"wires":[]},{"id":"ecb5fce2.ce1dc","type":"function","z":"dfef6fbd.55491","name":"計(jì)數(shù)器","func":"var count = context.get('count')||0;\n//如果count不存在就初始化為0，已存在則獲取count的值\ncount += 1;\ncontext.set('count',count);\n//執(zhí)行完+1操作以后保存count的值\nmsg.payload = count;\nreturn msg;","outputs":1,"noerr":0,"x":880,"y":160,"wires":[["7e2fd11b.d4b4"]]}]

5.4.2 使用flow在不同節(jié)點(diǎn)之間傳遞參數(shù)

　　在5.4.1小節(jié)中，函數(shù)節(jié)點(diǎn)計(jì)數(shù)器實(shí)現(xiàn)了用’count’來(lái)保存數(shù)據(jù)的方法，那么這個(gè)’count’里邊的內(nèi)容，能否被別的節(jié)點(diǎn)使用？我們來(lái)嘗試一下。
　　在上一章節(jié)的基礎(chǔ)上進(jìn)行修改，添加計(jì)數(shù)器2，并做如下修改：


　　如果計(jì)數(shù)器2可以使用’count’的內(nèi)容，那么payload里的內(nèi)容應(yīng)該是遞增的數(shù)據(jù)。然而，部署以后，觀察實(shí)驗(yàn)現(xiàn)象，可以發(fā)現(xiàn)OUT2的內(nèi)容并沒(méi)有變化。這說(shuō)明計(jì)數(shù)器2沒(méi)有辦法獲取’count’里的數(shù)據(jù)。

　　細(xì)心的讀者可以發(fā)現(xiàn)，在context的API里，有這么一句解釋：
context.get(..) : 獲取一個(gè)節(jié)點(diǎn)范圍內(nèi)的上下文屬性
　　也就是使用context屬性只能影響一個(gè)節(jié)點(diǎn)范圍內(nèi)。然而在實(shí)際的應(yīng)用中，不同的節(jié)點(diǎn)之間可能會(huì)用到同一個(gè)變量，也就是說(shuō)，有一個(gè)“全局變量”，該如何傳遞？
　　我們查閱了函數(shù)的API，找到了flow的context用法，地址是

https://nodered.org/docs/writing-functions flow.get(..) : 獲得流作用域上下文屬性 flow.set(..) : 設(shè)置流作用域上下文屬性 flow.keys(..) : 返回所有流作用域上下文屬性鍵的列表

　　修改為“計(jì)數(shù)器”節(jié)點(diǎn)

　　修改“計(jì)數(shù)器2”節(jié)點(diǎn)

　　部署并點(diǎn)擊inject節(jié)點(diǎn)的輸入按鈕，看到現(xiàn)象如下

　　這說(shuō)明計(jì)數(shù)器2獲取到了計(jì)數(shù)器中的count值，也就是通過(guò)flow.set與flow.get實(shí)現(xiàn)了不同節(jié)點(diǎn)的參數(shù)傳遞。
流程分析如下：

　　流的信息保存在這里：

[{"id":"d5052172.91827","type":"inject","z":"a1f259d6.8791a8","name":"","topic":"","payload":"1","payloadType":"num","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":140,"y":180,"wires":[["9ddd2b2f.536d28"]]},{"id":"811f3cdb.bf65b","type":"debug","z":"a1f259d6.8791a8","name":"OUT1","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","x":530,"y":180,"wires":[]},{"id":"9ddd2b2f.536d28","type":"function","z":"a1f259d6.8791a8","name":"計(jì)數(shù)器","func":"var count = context.get('count')||0;\n//如果count不存在就初始化為0，已存在則獲取count的值\ncount += 1;\ncontext.set('count',count);\n//執(zhí)行完+1操作以后保存count的值\nflow.set('flowSave',count);\n//設(shè)置一個(gè)flowSave，來(lái)保存變量count的值\nmsg.payload = count;\nreturn msg;","outputs":1,"noerr":0,"x":330,"y":180,"wires":[["811f3cdb.bf65b","dbecc13a.c9642"]]},{"id":"dbecc13a.c9642","type":"function","z":"a1f259d6.8791a8","name":"計(jì)數(shù)器2","func":"var count = flow.get('flowSave')||0;\n//如果count不存在就初始化為0，已存在則獲取count的值\nmsg.payload = count;\nreturn msg;","outputs":1,"noerr":0,"x":450,"y":260,"wires":[["71a9791a.cd5f28"]]},{"id":"71a9791a.cd5f28","type":"debug","z":"a1f259d6.8791a8","name":"OUT2","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","x":610,"y":260,"wires":[]}]

5.4.3 使用flow實(shí)現(xiàn)計(jì)時(shí)器

　　使用flow的屬性在不同的節(jié)點(diǎn)之間傳遞參數(shù)，這個(gè)功能十分有用。接下來(lái)嘗試使用flow實(shí)現(xiàn)一個(gè)節(jié)點(diǎn)執(zhí)行時(shí)間的計(jì)數(shù)器。
　　在JS中，可以使用Data對(duì)象的getTime方法獲取從1970年1月1日至今的毫秒數(shù)。跟時(shí)間戳得到的數(shù)據(jù)類似。在開(kāi)始節(jié)點(diǎn)和結(jié)束節(jié)點(diǎn)分別獲取時(shí)間，兩個(gè)值的差就是這兩個(gè)節(jié)點(diǎn)之間所用的時(shí)間了。
　　另外，需要一個(gè)延時(shí)節(jié)點(diǎn)來(lái)放在兩個(gè)計(jì)時(shí)節(jié)點(diǎn)之間。在功能控件里恰好有一個(gè)名為“delay”的控件滿足要求。它可以控制消息通過(guò)自己的時(shí)間或者限制它的傳遞速度。我們會(huì)使用它的隨機(jī)延時(shí)的功能。
　　這次我們先來(lái)畫(huà)一個(gè)流程圖來(lái)分析思路。所謂“謀定而后動(dòng)”，在編程里也是一個(gè)好習(xí)慣。

　　這是開(kāi)始時(shí)間的設(shè)置

　　這是結(jié)束時(shí)間的設(shè)置

　　這是delay節(jié)點(diǎn)的設(shè)置

　　整個(gè)流連線如下。完成以后部署并點(diǎn)擊inject節(jié)點(diǎn)的輸入按鈕

　　可以看到，delay節(jié)點(diǎn)出現(xiàn)了一個(gè)藍(lán)色的標(biāo)記，以及表示時(shí)間的數(shù)字。這就是節(jié)點(diǎn)的狀態(tài)status。

　　調(diào)試窗口信息如下

　　這是代碼，懶得自己輸入的可以直接導(dǎo)入看結(jié)果。

[{"id":"710e935.672cf6c","type":"inject","z":"b0555ded.82baa","name":"","topic":"","payload":"","payloadType":"date","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":150,"y":200,"wires":[["c3b7267d.1578c8"]]},{"id":"8bc81259.86e39","type":"debug","z":"b0555ded.82baa","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","x":560,"y":200,"wires":[]},{"id":"c3b7267d.1578c8","type":"function","z":"b0555ded.82baa","name":"開(kāi)始時(shí)間","func":"flow.set('stratTime',new Date().getTime());\n//使用data對(duì)象的getTime方法獲取開(kāi)始時(shí)間，\n//并存到'startTime'里\nreturn msg;","outputs":1,"noerr":0,"x":260,"y":280,"wires":[["28cea295.2be12e"]]},{"id":"9152870f.6bf4e8","type":"function","z":"b0555ded.82baa","name":"結(jié)束時(shí)間","func":"var currentTime = new Date().getTime();\n//獲取當(dāng)前時(shí)間\nvar stratTime = flow.get('stratTime',stratTime);\n//用flow.get獲取之間節(jié)點(diǎn)儲(chǔ)存的開(kāi)始時(shí)間\nvar timeElapsed = (currentTime - stratTime)/1000;\n//計(jì)算時(shí)間差并從毫秒轉(zhuǎn)換為秒\nmsg.payload = \"逝去的時(shí)間是: \"+timeElapsed+\"s\";\nreturn msg;","outputs":1,"noerr":0,"x":460,"y":280,"wires":[["8bc81259.86e39"]]},{"id":"28cea295.2be12e","type":"delay","z":"b0555ded.82baa","name":"","pauseType":"random","timeout":"5","timeoutUnits":"seconds","rate":"1","nbRateUnits":"1","rateUnits":"second","randomFirst":"1","randomLast":"5","randomUnits":"seconds","drop":false,"x":350,"y":200,"wires":[["9152870f.6bf4e8"]]}]

5.4.4 使用全局變量

　　全局變量名為global，它與flow功能類似，但是作用域比f(wàn)low大，并且，即便重新部署，global儲(chǔ)存的值也不會(huì)丟失。以下是global的API。

global.get(..) ：獲取全局范圍的上下文屬性 global.set(..) ：設(shè)置全局范圍的上下文屬性 global.keys(..) ：返回所有全局作用域上下文屬性鍵的列表

　　在5.4.3中見(jiàn)到的例子使用global也完全可以實(shí)現(xiàn)，只需要把里邊所有的“flow”換成“global”就可以，由于太簡(jiǎn)單，就不演示了。Flow的作用于只局限于同一個(gè)流，此處做一點(diǎn)flow做不到的事情——流之間的數(shù)據(jù)傳遞。程序設(shè)計(jì)思路如下：

　　整個(gè)流程如下設(shè)計(jì)

　　開(kāi)始時(shí)間與當(dāng)前時(shí)間分別設(shè)計(jì)如下


　　完成以后部署，并先點(diǎn)擊開(kāi)始時(shí)間的輸入按鈕，再點(diǎn)擊當(dāng)前時(shí)間的輸入按鈕。調(diào)試窗口現(xiàn)象如下：

　　從現(xiàn)象中可以看出來(lái)雖然兩個(gè)流沒(méi)有直接連接，但是第二個(gè)流仍然獲取了在第一個(gè)流中設(shè)置的變量。說(shuō)明實(shí)驗(yàn)成功。
接下來(lái)，觀察重新部署時(shí)，global變量能否保存。為節(jié)點(diǎn)做一些無(wú)關(guān)緊要的修改，例如out改為OUT，以便能夠點(diǎn)擊“部署”按鈕。

　　部署完成以后，不要點(diǎn)擊“開(kāi)始時(shí)間”的輸入按鈕，直接點(diǎn)擊“當(dāng)前時(shí)間”的輸入按鈕，可以觀察到如下的現(xiàn)象。

　　逝去的時(shí)間并沒(méi)有被重置，說(shuō)明重新部署不影響global的內(nèi)容。
　　程序的代碼保存在這里

[{"id":"eaf64e67.5277","type":"inject","z":"3769aa0d.6513d6","name":"開(kāi)始時(shí)間","topic":"","payload":"","payloadType":"date","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":140,"y":220,"wires":[["8a1f7741.6eb3b8"]]},{"id":"d6468738.ed2948","type":"debug","z":"3769aa0d.6513d6","name":"startTime","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","x":460,"y":220,"wires":[]},{"id":"8a1f7741.6eb3b8","type":"function","z":"3769aa0d.6513d6","name":"開(kāi)始時(shí)間","func":"global.set('stratTime',new Date().getTime());\n//使用data對(duì)象的getTime方法獲取開(kāi)始時(shí)間，\n//并存到'startTime'里\nreturn msg;","outputs":1,"noerr":0,"x":280,"y":220,"wires":[["d6468738.ed2948"]]},{"id":"4c55cdab.648834","type":"function","z":"3769aa0d.6513d6","name":"當(dāng)前時(shí)間","func":"var currentTime = new Date().getTime();\n//獲取當(dāng)前時(shí)間\nvar stratTime = global.get('stratTime',stratTime);\n//用global.get獲取之間節(jié)點(diǎn)儲(chǔ)存的開(kāi)始時(shí)間\nvar timeElapsed = (currentTime - stratTime)/1000;\n//計(jì)算時(shí)間差并從毫秒轉(zhuǎn)換為秒\nmsg.payload = \"逝去的時(shí)間是: \"+timeElapsed+\"s\";\nreturn msg;","outputs":1,"noerr":0,"x":280,"y":300,"wires":[["c5123924.d3f928"]]},{"id":"9f83e717.eaf888","type":"inject","z":"3769aa0d.6513d6","name":"當(dāng)前時(shí)間","topic":"","payload":"","payloadType":"date","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":120,"y":300,"wires":[["4c55cdab.648834","357d85e7.a522ba"]]},{"id":"c5123924.d3f928","type":"debug","z":"3769aa0d.6513d6","name":"OUT","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","x":440,"y":300,"wires":[]},{"id":"357d85e7.a522ba","type":"debug","z":"3769aa0d.6513d6","name":"crrentTime","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","x":280,"y":400,"wires":[]}]

　　接下來(lái)，可以試一試不同的頁(yè)面內(nèi)，global的數(shù)值能否傳遞。新建一個(gè)頁(yè)面。點(diǎn)擊這個(gè)加號(hào)：

　　把第一個(gè)流放在“開(kāi)始的時(shí)間的流”標(biāo)簽下。第二個(gè)流放在“當(dāng)前時(shí)間的流”標(biāo)簽下。


　　部署，并先后點(diǎn)擊開(kāi)始時(shí)間與當(dāng)前時(shí)間的輸入按鈕，可以在調(diào)試窗口看到如下現(xiàn)象，說(shuō)明，即便是跨標(biāo)簽頁(yè)，global的數(shù)據(jù)仍可以傳遞。

　　另外，我在官方的博客見(jiàn)到了沒(méi)有使用set與get方法的另外一種寫(xiě)法，經(jīng)過(guò)實(shí)驗(yàn)也可以使用，把它寫(xiě)在這里。

context.global.startTime = new Date().getTime(); //global.set('stratTime',new Date().getTime()); var timeElapsed = (currentTime - context.global.startTime)/1000; //var stratTime = global.get('stratTime',stratTime); //var timeElapsed = (currentTime - stratTime)/1000;

5.5 函數(shù)控件的其它功能

　　函數(shù)控件的功能強(qiáng)大，甚至可以用函數(shù)控件實(shí)現(xiàn)其它所有功能控件的功能。在函數(shù)空間中，除了可以調(diào)用JS自帶的各種方法以外，含有一些node-red特有的API可以使用，我把它寫(xiě)在這里

node.id :函數(shù)節(jié)點(diǎn)的ID，在0.19版本添加 node.name :函數(shù)節(jié)點(diǎn)的名字，在0.19版本增加 node.log(..) : 記錄一條消息 node.warn(..) : 記錄一條警告消息 node.error(..) : 記錄一條錯(cuò)誤消息 node.debug(..) :記錄一條調(diào)試消息 node.trace(..) : 記錄跟蹤消息 node.on(..) : 注冊(cè)一個(gè)事件處理函數(shù) node.status(..) : 更新節(jié)點(diǎn)的狀態(tài) node.send(..) : 發(fā)送消息

　　這其中從log到trace都是用來(lái)向命令換輸出信息的，由于用法十分簡(jiǎn)單，就不講解了。

5.5.1 使用send方法發(fā)送數(shù)據(jù)

　　在5.2.3小節(jié)時(shí)，我們遇到一個(gè)問(wèn)題：如果“apple”既滿足條件1，又滿足條件3，但是條件1執(zhí)行return 的操作以后，條件3就不再執(zhí)行了，有沒(méi)有既可以發(fā)送數(shù)據(jù)，又不會(huì)結(jié)束函數(shù)的方法？當(dāng)然有。我們查詢了節(jié)點(diǎn)可以調(diào)用的API，發(fā)現(xiàn)有send函數(shù)，滿足我們的要求。
　　查一下之前的代碼，把“判斷主題”節(jié)點(diǎn)做如下修改

　　然后部署并觀察現(xiàn)象，可以發(fā)現(xiàn)，當(dāng)點(diǎn)擊apple的輸入按鈕時(shí)，OUT1與OUT3都可以收到消息，說(shuō)明實(shí)驗(yàn)成功。

　　代碼如下

[{"id":"aaa307ba.874e58","type":"function","z":"b0555ded.82baa","name":"判斷主題","func":"if (msg.topic === \"apple\") {\n node.send([ msg, null, null]);\n} \nif(msg.topic === \"banana\"){\n node.send( [ null, msg, null]);\n}\nif(msg.topic.indexOf(\"e\") != -1){\n node.send([null,null, msg ]);\n}\n","outputs":3,"noerr":0,"x":360,"y":300,"wires":[["e8ac6685.9b2a48"],["503899c3.750508"],["1053e26d.f8c7ae"]]},{"id":"8e22df59.c7795","type":"inject","z":"b0555ded.82baa","name":"","topic":"apple","payload":"apple","payloadType":"str","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":150,"y":240,"wires":[["aaa307ba.874e58"]]},{"id":"1692dfa1.47a2a","type":"inject","z":"b0555ded.82baa","name":"","topic":"banana","payload":"banana","payloadType":"str","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":160,"y":300,"wires":[["aaa307ba.874e58"]]},{"id":"bb012d65.92486","type":"inject","z":"b0555ded.82baa","name":"","topic":"orange","payload":"orange","payloadType":"str","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":160,"y":360,"wires":[["aaa307ba.874e58"]]},{"id":"e8ac6685.9b2a48","type":"debug","z":"b0555ded.82baa","name":"OUT1","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","x":550,"y":240,"wires":[]},{"id":"503899c3.750508","type":"debug","z":"b0555ded.82baa","name":"OUT2","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","x":550,"y":300,"wires":[]},{"id":"1053e26d.f8c7ae","type":"debug","z":"b0555ded.82baa","name":"OUT3","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","x":550,"y":360,"wires":[]}]

5.5.2 流程之間傳遞函數(shù)

　　Context元素除了可以傳遞變量以外，也可以傳遞函數(shù)。我們?cè)诹?中新建一個(gè)名為hello的函數(shù)，在流2中調(diào)用它。
　　流1的函數(shù)節(jié)點(diǎn)

　　流2的函數(shù)節(jié)點(diǎn)

　 先點(diǎn)擊IN1的輸入按鈕，再點(diǎn)擊IN2的輸入按鈕，可以看到OUT2中打印出了hello world，其中的“hello”是通過(guò)調(diào)用流1 的hello()函數(shù)打印出來(lái)的，說(shuō)明實(shí)驗(yàn)成功了。

　　代碼保存在這里

[{"id":"eaf64e67.5277","type":"inject","z":"3769aa0d.6513d6","name":"IN1","topic":"","payload":"","payloadType":"date","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":210,"y":160,"wires":[["1012b4b4.a746fb"]]},{"id":"d6468738.ed2948","type":"debug","z":"3769aa0d.6513d6","name":"OUT1","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","x":530,"y":160,"wires":[]},{"id":"1012b4b4.a746fb","type":"function","z":"3769aa0d.6513d6","name":"hello","func":"context.global.hello = function(){return \"hello\"};\nmsg.payload = context.global.hello();\nreturn msg;","outputs":1,"noerr":0,"x":370,"y":160,"wires":[["d6468738.ed2948"]]},{"id":"8331681d.a15558","type":"function","z":"3769aa0d.6513d6","name":"+world","func":"msg.payload = context.global.hello() + \" World\";\nreturn msg;","outputs":1,"noerr":0,"x":350,"y":260,"wires":[["8214b226.35f87"]]},{"id":"eff72cea.339ae","type":"inject","z":"3769aa0d.6513d6","name":"IN2","topic":"","payload":"","payloadType":"date","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":190,"y":260,"wires":[["8331681d.a15558"]]},{"id":"8214b226.35f87","type":"debug","z":"3769aa0d.6513d6","name":"OUT2","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","x":520,"y":260,"wires":[]}]

5.5.3 使用狀態(tài)標(biāo)志

　　在5.4.3小節(jié)時(shí)，我們第一次使用delay節(jié)點(diǎn)，用于產(chǎn)生一個(gè)隨機(jī)數(shù)。此節(jié)點(diǎn)在在運(yùn)行的時(shí)候顯示出了一個(gè)表示時(shí)間的字符，顯示這個(gè)隨機(jī)的時(shí)間是多少。我覺(jué)得這個(gè)功能很有用，很直觀的可以顯示出我們感興趣的一些數(shù)據(jù)或狀態(tài)，可以省去到處用debug節(jié)點(diǎn)打印的煩惱。翻看函數(shù)節(jié)點(diǎn)的API，正好有一條可以用來(lái)顯示狀態(tài)：
　　node.status(..) : 更新節(jié)點(diǎn)的狀態(tài)

　　我們來(lái)研究一下如何使用。
　　首先要搭建一個(gè)可變的輸入信息，并且要持續(xù)一段時(shí)間，避免狀態(tài)變得太快看不到。相信詳細(xì)學(xué)過(guò)函數(shù)控件用法以后，對(duì)于聰明的你來(lái)說(shuō)，這一定不是難事。——用函數(shù)節(jié)點(diǎn)+delay節(jié)點(diǎn)可以實(shí)現(xiàn)。先拖拽節(jié)點(diǎn)，形成數(shù)據(jù)流。

　　第一個(gè)函數(shù)節(jié)點(diǎn)用于發(fā)送5個(gè)數(shù)字：

　　Delay節(jié)點(diǎn)用于限制數(shù)據(jù)包的速度，每秒一條。

　　如此就能實(shí)現(xiàn)，第二個(gè)函數(shù)節(jié)點(diǎn)每秒接收到一個(gè)數(shù)字。

　　第二個(gè)函數(shù)節(jié)點(diǎn)的代碼如下：

node.status({fill:"green",shape:"dot",text:"Received "+msg.payload}); return msg;

　　也很好理解：填充綠色的點(diǎn)，文本顯示“Received + 載荷”，只是格式死板一點(diǎn)，照著填寫(xiě)，不要遺漏標(biāo)點(diǎn)或拼寫(xiě)錯(cuò)誤。
接下來(lái)點(diǎn)擊inject的輸入按鈕，可以在調(diào)試窗口看到每隔一秒收到一個(gè)數(shù)據(jù)。這都是意料中的現(xiàn)象。

　　同時(shí)，第二個(gè)函數(shù)節(jié)點(diǎn)也能顯示出一些信息。綠色的點(diǎn)，以及顯示內(nèi)容都是我們代碼中自己編寫(xiě)的，所以，任務(wù)完成。


　　代碼在這里

[{"id":"5e91200b.6cd0c","type":"inject","z":"3769aa0d.6513d6","name":"","topic":"","payload":"","payloadType":"date","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":140,"y":120,"wires":[["27878fd7.889b1"]]},{"id":"27878fd7.889b1","type":"function","z":"3769aa0d.6513d6","name":"send1-5","func":"for (var i=0; i<5 ; i++){\n node.send({payload:i});\n}\nreturn null;","outputs":1,"noerr":0,"x":240,"y":200,"wires":[["b99e8ad0.ce0d28"]]},{"id":"4705bd05.3042f4","type":"debug","z":"3769aa0d.6513d6","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","x":630,"y":120,"wires":[]},{"id":"b99e8ad0.ce0d28","type":"delay","z":"3769aa0d.6513d6","name":"","pauseType":"rate","timeout":"5","timeoutUnits":"seconds","rate":"1","nbRateUnits":"1","rateUnits":"second","randomFirst":"1","randomLast":"5","randomUnits":"seconds","drop":false,"x":370,"y":120,"wires":[["1d46ef67.107e81"]]},{"id":"1d46ef67.107e81","type":"function","z":"3769aa0d.6513d6","name":"received1-5","func":"node.status({fill:\"green\",shape:\"dot\",text:\"Received \"+msg.payload});\nreturn msg;","outputs":1,"noerr":0,"x":510,"y":200,"wires":[["4705bd05.3042f4"]]}]

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