如何在没有 eval 的情况下编写这段 JavaScript 代码?
var typeOfString = eval("typeof " + that.modules[modName].varName);
if (typeOfString !== "undefined") {
doSomething();
}
重点是我要检查的 var 的名称在字符串中。
也许这很简单,但我不知道怎么做。
编辑:感谢您到目前为止提供的非常有趣的答案。我会按照您的建议并将其集成到我的代码中并进行一些测试和报告。可能需要一段时间。
Edit2: 我又看了一眼 jar 头,也许我给你看一张更大的图画更好。感谢专家们解释的这么漂亮,代码越多越好:
MYNAMESPACE.Loader = ( function() {
function C() {
this.modules = {};
this.required = {};
this.waitCount = 0;
this.appendUrl = '';
this.docHead = document.getElementsByTagName('head')[0];
}
function insert() {
var that = this;
//insert all script tags to the head now!
//loop over all modules:
for (var modName in this.required) {
if(this.required.hasOwnProperty(modName)){
if (this.required[modName] === 'required') {
this.required[modName] = 'loading';
this.waitCount = this.waitCount + 1;
this.insertModule(modName);
}
}
}
//now poll until everything is loaded or
//until timout
this.intervalId = 0;
var checkFunction = function() {
if (that.waitCount === 0) {
clearInterval(that.intervalId);
that.onSuccess();
return;
}
for (var modName in that.required) {
if(that.required.hasOwnProperty(modName)){
if (that.required[modName] === 'loading') {
var typeOfString = eval("typeof " + that.modules[modName].varName);
if (typeOfString !== "undefined") {
//module is loaded!
that.required[modName] = 'ok';
that.waitCount = that.waitCount - 1;
if (that.waitCount === 0) {
clearInterval(that.intervalId);
that.onSuccess();
return;
}
}
}
}
}
};
//execute the function twice a second to check if all is loaded:
this.intervalId = setInterval(checkFunction, 500);
//further execution will be in checkFunction,
//so nothing left to do here
}
C.prototype.insert = insert;
//there are more functions here...
return C;
}());
var myLoader = new MYNAMESPACE.Loader();
//some more lines here...
myLoader.insert();
编辑 3:
为了简单起见,我计划将它放在变量 MYNAMESPACE.loadCheck 的全局命名空间中,所以结果将是,结合不同的答案和评论:
if (MYNAMESPACE.loadCheck.modules[modName].varName in window) {
doSomething();
}
当然,我必须更新提到“varName”的 Loader 类。
最佳答案
在 JS 中,每个变量都是一个属性,如果你不知道它是谁的属性,它就是一个 window
属性,所以我想,在你的情况下,这可能有效:
var typeOFString = typeof window[that.modules[modName].varName]
if (typeOFString !== "undefined") {
doSomething();
}
关于javascript - 如何在没有 eval 的情况下编写这段 JavaScript 代码?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/2600420/