将单个事件附加到存储在数组中的多个元素，原生 JS

发布于 2024-12-09 09:06:10 字数 487 浏览 0 评论 0原文

每个人都在建议一些框架，但我想知道如何在原生 JavaScript 中完成它。我已经尝试过这段代码和其他一些东西，没有效果。似乎我不知道一些基本的概念。任何帮助将不胜感激。

window.onload = function() {
    var trCurrent
    var main = document.getElementById('main');
    var tr = main.getElementsByTagName('tr');
    function hl() {
            trCurrent.setAttribute('class', 'highlight');
    };
    for (var x = 0; x < tr.lenght; x++) { 
        trCurrent = tr[x];
        trCurrent.addEventListener ('mousedown', hl, false);
    }
};

原文

Everyone is suggesting some framework, but I'd like to know how it can be done in native JavaScript. I've tried this code and some other things, no effect. Seems that I'm unaware of some basic underlying concept. Any help would be appreciated.

window.onload = function() {
    var trCurrent
    var main = document.getElementById('main');
    var tr = main.getElementsByTagName('tr');
    function hl() {
            trCurrent.setAttribute('class', 'highlight');
    };
    for (var x = 0; x < tr.lenght; x++) { 
        trCurrent = tr[x];
        trCurrent.addEventListener ('mousedown', hl, false);
    }
};

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枯叶蝶 2024-12-16 09:06:10

您必须在函数h1中将trCurrent更改为this，因为trCurrent指向最后定义的TR元素（ trCurrent = tr[x] 表示高 x）。
使用 .length 而不是 .lenght。

最终代码：

window.onload = function() {
    var main = document.getElementById('main');
    var tr = main.getElementsByTagName('tr');
    function hl() {
        this.setAttribute('class', 'highlight');
    };
    for (var x = 0; x < tr.length; x++) { 
        tr[x].addEventListener ('mousedown', hl, false);
    }
};

如果您想使用在循环期间可能发生变化的变量，则需要将主体包装在（匿名）函数中：

window.onload = function() {
    var main = document.getElementById('main');
    var tr = main.getElementsByTagName('tr');
    for (var x = 0; x < tr.length; x++) {

        (function(trCurrent){ //Anonymous wrapper, first argument: `trCurrent`
            function hl() {
                trCurrent.setAttribute('class', 'highlight');
            };
            trCurrent.addEventListener ('mousedown', hl, false);
        })(tr[x]); //Passing a reference to `tr[x]`
    }
};

You have to change trCurrent to this at your function h1, becayse trCurrent points to the last defined TR element (trCurrent = tr[x] for a high x).
Use .length instead of .lenght.

Final code:

window.onload = function() {
    var main = document.getElementById('main');
    var tr = main.getElementsByTagName('tr');
    function hl() {
        this.setAttribute('class', 'highlight');
    };
    for (var x = 0; x < tr.length; x++) { 
        tr[x].addEventListener ('mousedown', hl, false);
    }
};

If you want to use an variable which is subject to change during a loop, it's required to wrap the body in an (anonymous) function:

window.onload = function() {
    var main = document.getElementById('main');
    var tr = main.getElementsByTagName('tr');
    for (var x = 0; x < tr.length; x++) {

        (function(trCurrent){ //Anonymous wrapper, first argument: `trCurrent`
            function hl() {
                trCurrent.setAttribute('class', 'highlight');
            };
            trCurrent.addEventListener ('mousedown', hl, false);
        })(tr[x]); //Passing a reference to `tr[x]`
    }
};

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