Question

我刚从一本书上复制了这段:

window.onload = init;
function init() {
var button = document.getElementById("addButton");
button.onclick = handleButtonClick();
}
function handleButtonClick() {
alert("Button has been clicked");
}

问题是,当我装入页面时出现警报,而不是当我点击按钮时出现警报。有人为什么吗?

Answer 1

变动变动

but至n.onclick = handleBut至nClick();

至

but至n.onclick = handleBut至nClick;

(没有 () 。 )

Your original line, but至n.onclick = handleBut至nClick(); calls the handleBut至nClick function and then assigns its return value 至 but至n.onclick. It s exactly like

var a = foo();

...which calls foo and then assigns its return value 至 a.

You don t want 至 do that, you just want 至 assign the function reference 至 onclick. So you refer 至 the function by its name, without calling it (so, without the ()).

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