blocks|key|1454566|text|有一个术语功能与变量提升。当您创建这样一个function和一个带有var的变量时，它们移动到了所有变量的顶部。但functions在first出现在variables之前。因此，当您调用function时，它会看到function，而不会看到variable。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|BOLD|entityRanges|data|1454567|Engine会将您的代码解析为此，并逐行执行。所以它没有看到variable。|1454568|function+__getUserByRmId(rmId)+{
++++console.log(firstCallFlag);+
}

__getUserByRmId('sun1')

var+firstCallFlag+=+1;|code-block|syntax|javascript|1454569|您需要在变量声明之后调用函数。|1454570|​|1454571|var+firstCallFlag+=+1;

__getUserByRmId('sun1');

function+__getUserByRmId(rmId)+{
++++console.log(firstCallFlag);+
}++++++++|1454572|1454573|entityMap|0|LINK|mutability|MUTABLE|url|http://adripofjavascript.com/blog/drips/variable-and-function-hoisting^0|L|8|Y|3|1L|9|23|9|2M|8|30|8|3E|8|1V|5|5|7|0|0|U|8|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|12|8|@$9|13|A|14|B|C]|$9|15|A|16|B|C]|$9|17|A|18|B|C]|$9|19|A|1A|B|C]|$9|1B|A|1C|B|C]|$9|1D|A|1E|B|C]|$9|1F|A|1G|B|C]|$9|1H|A|1I|B|D]]|E|@$9|1J|A|1K|1|1L]]|F|$]]|$1|G|3|H|5|6|7|1M|8|@$9|1N|A|1O|B|C]]|E|@]|F|$]]|$1|I|3|J|5|K|7|1P|8|@]|E|@]|F|$L|M]]|$1|N|3|O|5|6|7|1Q|8|@]|E|@]|F|$]]|$1|P|3|Q|5|6|7|1R|8|@]|E|@]|F|$]]|$1|R|3|S|5|K|7|1S|8|@]|E|@]|F|$L|M]]|$1|T|3|Q|5|6|7|1T|8|@]|E|@]|F|$]]|$1|U|3|-4|5|6|7|1U|8|@]|E|@]|F|$]]]|V|$W|$5|X|Y|Z|F|$10|11]]]]

<p>There is a term <a href="http://adripofjavascript.com/blog/drips/variable-and-function-hoisting" rel="nofollow noreferrer"><strong>function and variable hoisting</strong></a>. When you create a <code>function</code> like that and a variable with <code>var</code>, they moved to the top of of all. But the <code>functions</code> are hoisted <strong>first</strong> before <code>variables</code>. So when you call the <code>function</code>, it sees the <code>function</code> , but doesn't see the <code>variable</code>. </p>

<p>Engine parses your code to this and executes line by line. So it doesn't see the <code>variable</code>.</p>

<pre><code>function __getUserByRmId(rmId) {
    console.log(firstCallFlag); 
}

__getUserByRmId('sun1')

var firstCallFlag = 1;
</code></pre>

<p>You need to call your function after the variable declaration</p>

<p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
<div class="snippet-code">
<pre class="snippet-code-js lang-js prettyprint-override"><code>var firstCallFlag = 1;

__getUserByRmId('sun1');

function __getUserByRmId(rmId) {
    console.log(firstCallFlag); 
}        </code></pre>
</div>
</div>
</p>


blocks|key|1652262|text|声明变量后调用函数。函数将首先提升变量，然后再提升变量。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1652263|​|1652264|var+firstCallFlag+=+1;
function+__getUserByRmId(rmId)+{
++++console.log(firstCallFlag);+
}
__getUserByRmId('sun1');|code-block|syntax|javascript|1652265|1652266|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|M|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|N|8|@]|9|@]|A|$G|H]]|$1|I|3|C|5|6|7|O|8|@]|9|@]|A|$]]|$1|J|3|-4|5|6|7|P|8|@]|9|@]|A|$]]]|K|$]]

<p>Call the function after declaring the variable. Function will hoist first and then the variables.</p>

<p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
<div class="snippet-code">
<pre class="snippet-code-js lang-js prettyprint-override"><code>var firstCallFlag = 1;
function __getUserByRmId(rmId) {
    console.log(firstCallFlag); 
}
__getUserByRmId('sun1');</code></pre>
</div>
</div>
</p>


blocks|key|488963|text|这是因为变量是在调用函数之后定义的。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|488964|你可以做到这一点。看起来不错。|488965|var+firstCallFlag+=+1;
__getUserByRmId('sun1')

function+__getUserByRmId(rmId)+{
++++console.log(firstCallFlag);+
}|code-block|syntax|javascript|488966|顺便说一句，提升是JavaScript的默认行为，将所有声明移到当前作用域的顶部。所以，像这样的东西应该能起作用。|offset|length|style|BOLD|488967|+firstCallFlag+=1+;
__getUserByRmId('sun1')

function+__getUserByRmId(rmId)+{
++++console.log(firstCallFlag);+
}
var+firstCallFlag;|488968|但是，JavaScript初始化没有悬挂。因此，下面这样的代码将考虑未定义的变量firstCallFlag。|488969|__getUserByRmId('sun1')

function+__getUserByRmId(rmId)+{
++++console.log(firstCallFlag);+
}
var+firstCallFlag+=+1;+|488970|entityMap^0|0|0|0|6|2|P|C|0|0|3|H|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|X|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|Y|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|Z|8|@$K|10|L|11|M|N]|$K|12|L|13|M|N]]|9|@]|A|$]]|$1|O|3|P|5|F|7|14|8|@]|9|@]|A|$G|H]]|$1|Q|3|R|5|6|7|15|8|@$K|16|L|17|M|N]]|9|@]|A|$]]|$1|S|3|T|5|F|7|18|8|@]|9|@]|A|$G|H]]|$1|U|3|-4|5|6|7|19|8|@]|9|@]|A|$]]]|V|$]]

<p>This is because the variable is defined after the function is called.</p>

<p>You can do this. It will work.</p>

<pre><code>var firstCallFlag = 1;
__getUserByRmId('sun1')

function __getUserByRmId(rmId) {
    console.log(firstCallFlag); 
}
</code></pre>

<p>By the way, <strong>hoisting</strong> is JavaScript's default behavior of <strong>moving all declarations to the top of the current scope</strong>. So, something like this should work.</p>

<pre><code> firstCallFlag =1 ;
__getUserByRmId('sun1')

function __getUserByRmId(rmId) {
    console.log(firstCallFlag); 
}
var firstCallFlag;
</code></pre>

<p>However, <strong>JavaScript Initializations are Not Hoisted</strong>. Thus, the code like below will consider the variable firstCallFlag undefined.</p>

<pre><code>__getUserByRmId('sun1')

function __getUserByRmId(rmId) {
    console.log(firstCallFlag); 
}
var firstCallFlag = 1; 
</code></pre>


blocks|key|1652311|text|​|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1652312|var+firstCallFlag+=+1;
function+__getUserByRmId(rmId)+{
++++console.log(firstCallFlag);+
}
__getUserByRmId('sun1');|code-block|syntax|javascript|1652313|1652314|因为您必须首先定义变量"firstCallFlag“，然后调用javascript中的__getUserByRmId('sun1');....variable提升函数。|offset|length|style|CODE|1652315|entityMap^0|0|0|0|17|O|0^^$0|@$1|2|3|4|5|6|7|P|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|Q|8|@]|9|@]|A|$E|F]]|$1|G|3|4|5|6|7|R|8|@]|9|@]|A|$]]|$1|H|3|I|5|6|7|S|8|@$J|T|K|U|L|M]]|9|@]|A|$]]|$1|N|3|-4|5|6|7|V|8|@]|9|@]|A|$]]]|O|$]]

<p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
<div class="snippet-code">
<pre class="snippet-code-js lang-js prettyprint-override"><code>var firstCallFlag = 1;
function __getUserByRmId(rmId) {
    console.log(firstCallFlag); 
}
__getUserByRmId('sun1');</code></pre>
</div>
</div>
</p>

<p>Its beacuse you have to define the variable "firstCallFlag " first and then call the function <code>__getUserByRmId('sun1');</code>....variable hoisting in javascript</p>


blocks|key|488984|text|如果您仍然希望使用相同的方法模式，而不在函数调用的顶部声明变量，则应该有如下所示的超时调用：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|488985|_getUserByRmId('sun1');

var+firstCallFlag+=+1;

function+__getUserByRmId(rmId)+{
+++setTimeout(function(){
++++++console.log(firstCallFlag);+
+++},1);++++++++
}|code-block|syntax|javascript|488986|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

<p>If you still want to work with the same pattern of approach without declaring the variable on top of function call, then you should have a timeout call like this:</p>

<pre><code>_getUserByRmId('sun1');

var firstCallFlag = 1;

function __getUserByRmId(rmId) {
   setTimeout(function(){
      console.log(firstCallFlag); 
   },1);        
}
</code></pre>


<p>As per me, every variable declared in javascript above functions treat as global. But in my case, i unable to access that variable show <code>undefined</code>. Here is <a href="https://jsfiddle.net/sc8achqn/" rel="nofollow noreferrer">jsfiddle</a></p>

<p><strong>code:</strong></p>

<pre><code>__getUserByRmId('sun1')
var firstCallFlag = 1;
function __getUserByRmId(rmId) {
    console.log(firstCallFlag); 
}
</code></pre>


Unable to access global variable in javascript

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

文章

问答

视频

学习中心

腾讯云实验室

直播

竞赛

腾讯云代码分析专区

腾讯iOA零信任安全管理系统专区

腾讯云架构师技术同盟交流圈

腾讯云数据库专区

腾讯云顾问专区

腾讯云原生专区

腾讯混元专区

腾讯云TCE专区

腾讯云Lighthouse专区

腾讯云HAI专区

腾讯云Edgeone专区

腾讯云存储专区

腾讯云智能专区

腾讯轻联专区 

腾讯云开发专区

TAPD专区

腾讯轻量云游戏服专区

腾讯云最具价值专家

腾讯云架构师技术同盟

腾讯云创作之星

腾讯云开发者先锋

腾讯云代码助手

云原生构建

TAPD 敏捷项目管理

Cloud Studio

SDK中心

API中心

命令行工具

涵盖代码开发、场景应用、自动测试全流程，助你从零构建专属AI助手

一站式MCP教程库，解锁AI应用新玩法

据我所知，上述函数中声明的每个变量都被视为全局变量。但在我的例子中，我无法访问显示undefined的变量。这是代码：__getUserByRmId('sun1')var firstCallFlag = 1;function __getUserByRmId(rmId) {    console.log(firstCal...

问无法访问javascript中的全局变量
EN

Stack Overflow用户

社区

活动

圈层

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问无法访问javascript中的全局变量EN