jQuery Javascript 函数和默认参数，不适用于 IE 和 Chrome
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/15178700/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Javascript Functions and default parameters, not working in IE and Chrome
提问by Talon
I created a function like this:
我创建了一个这样的函数：
function saveItem(andClose = false) {
}
It works fine in Firefox
它在 Firefox 中运行良好
In IE it gives this error on the console:
Expected ')'
在 IE 中，它在控制台上给出了这个错误：
Expected ')'
In Chrome it gives this error in the console:
Uncaught SyntaxError: Unexpected token =
在 Chrome 中，它会在控制台中出现此错误：
Uncaught SyntaxError: Unexpected token =
Both browsers mark the source of the error as the function creation line.
两个浏览器都将错误来源标记为函数创建行。
回答by juco
You can't do this, but you can instead do something like:
您不能这样做，但您可以执行以下操作：
function saveItem(andClose) {
if(andClose === undefined) {
andClose = false;
}
}
This is often shortened to something like:
这通常缩写为：
function setName(name) {
name = name || 'Bob';
}
Update
更新
The above is true for ECMAScript <= 5. ES6 has proposed Default parameters. So the above could instead read:
以上对于 ECMAScript <= 5 是正确的。 ES6 提出了Default parameters。所以上面可以改为：
function setName(name = 'Bob') {}
回答by the system
That's not a valid ECMAScript syntax, but it is a valid syntax for Mozilla's superset of features they add to their implementation of the language.
这不是有效的 ECMAScript 语法，但对于 Mozilla 的功能超集来说，这是一种有效的语法，它们添加到他们的语言实现中。
Default parameter assignment syntax is likelycoming in ECMAScript 6.
ECMAScript 6 中可能会出现默认参数分配语法。
回答by JRomero
Javascript does not allow a "default" specifier.
Javascript 不允许使用“默认”说明符。
A quick way of doing what you would want is changing:
做你想做的事情的一种快速方法是改变：
function saveItem(andClose = false) {
}
to the following:
到以下几点：
function saveItem(andClose) {
// this line will check if the argument is undefined, null, or false
// if so set it to false, otherwise set it to it's original value
var andClose = andClose || false;
// now you can safely use andClose
if (andClose) {
// do something
}
}
回答by Max Heiber
The code you provided won't run in Chrome < version 49: https://kangax.github.io/compat-table/es6/#test-default_function_parameters
您提供的代码不会在 Chrome < 49 版中运行：https: //kangax.github.io/compat-table/es6/#test-default_function_parameters
You used valid ECMAScript 2015 syntax:
您使用了有效的 ECMAScript 2015 语法：
In my opinion, the best way to use ES2015 features is to bundle assets with Browserifyor WebPack, with a step for using Babelto trans-compile ES2015 to ES5. That way you don't have to worry about that ES2015 browser compatibility chart. It's a pain to get started the first time, but worth it.
在我看来，使用 ES2015 特性的最好方法是将资产与Browserify或WebPack捆绑在一起，并有一个步骤是使用Babel将 ES2015 转编译为 ES5。这样你就不必担心 ES2015 浏览器兼容性图表。第一次开始很痛苦，但值得。
回答by Cédric Talpaert
In your case, you have an other alternative to be sure that your variable is a boolean:
在您的情况下，您有另一种选择来确保您的变量是布尔值：
function saveItem(andClose) {
var andClose = true == andClose;
// ...
}
Default value is undefined, and true == undefined=> false, so your default value will be false:)
默认值为undefined, 和true == undefined=> false，因此您的默认值为false:)
