我如何确保 Javascript 的“this"使用 setTimeout 时会引用对象吗? [英] How do I ensure that Javascript's "this" will refer to the object when using setTimeout?
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问题描述
<!doctype html>
<html>
<head>
<title>What is 'this'?</title>
<script>
function Obj(){
log('Obj instantiated');
}
Obj.prototype.foo = function (){
log('foo() says:');
log(this);
}
Obj.prototype.bar = function (){
log('bar() was triggered');
setTimeout(this.foo,300);
}
function log(v){console.log(v)}
var obj = new Obj();
</script>
</head>
<body>
<button onclick="obj.foo()">Foo</button>
<button onclick="obj.bar()">Bar</button>
</body>
</html>
这是控制台输出:
Obj instantiated
foo() says:
Obj {foo: function, bar: function}
bar() was triggered
foo() says:
Window {top: Window, window: Window, location: Location, external: Object, chrome: Object…}
因此，当它从 setTimeout 调用 obj.foo 时，'this' 会将所有权更改为 Window.我如何防止这种行为或正确处理这种行为?
So when it calls obj.foo from the setTimeout, 'this' changes ownership to the Window. How do I prevent that or properly work with that behavior?
谢谢
推荐答案
使用 .bind 调用.
setTimeout(this.foo.bind(this),300);
并非所有浏览器都支持它，但 MDN 上有一个 shim 并且 Underscore 也有 _.bind(...)
Not all browsers support it, but there is a shim on MDN and Underscore has _.bind(...) as well
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