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将链接方法附加到JavaScript中的元素集合

chaining element methods collections javascript

Hexagon Theory · 技术社区 · 17 年前

<div>a</div>
<div>b</div>
<div>c</div>
<script>
NodeList.prototype._ = function(s)
 {
    for (x = 0; x < this.length; x++)
     {
        eval('this[x]' + '.' + s);
     }
    return this;
 }
document.getElementsByTagName('div')._("style.backgroundColor = 'red'")._('innerHTML += x');
</script>

目前,它在Opera中工作得很好;正如预期的那样,正在对所有div元素调用u方法,然后对传递给它的字符串求值 到上面 每个元素依次。注意,该方法允许链接,并且已经演示过,调用u来附加预测的十每个元素的innerHTML的迭代器变量。

现在,两个问题。。。

首先,有没有更好的方法来解决这个问题?我一直希望我能做到 document.getElementsByTagName('div').style.backgroundColor = "red"; 但是,唉,它还没有成为现实。这就是为什么我首先要这样做,以及为什么我如此简洁地命名方法;我试图尽可能地模拟它。

NodeList 是 HTMLCollection

2 回复 | 直到 17 年前

Hexagon Theory 17 年前

我已经想出了一个可行的解决方案;使用这个方法来链式修改元素集合有什么本质上的坏处吗?

<script>
_ = function()
 {
    for (x = 0; x < arguments[0].length; x++)
     {
        for (y = 0; y < arguments[1].length; y++)
         {
            eval('arguments[0][x]' + '.' + arguments[1][y]);
         }
     }
 }
</script>

用法:

divs = document.getElementsByTagName('div');
_(divs, ["style.color = 'red'", "innerHTML += x"]);

Ruan Mendes 15 年前

/**
 * Sets a property on each of the elements in the list
 * @param {NodeList} list
 * @param {string} prop The name of property to be set, 
 *        e.g., 'style.backgroundColor', 'value'.
 * @param {mixed} value what to set the value to
 */
function setListProp( list, prop, value) {    
    for (var i = 0; i < list.length; i++) {
        setProp(list[i], prop, value);
    }
}

/**
 * Avoids the use of eval to set properties that may contain dots
 * Why avoid eval? eval is slow and could be dangerous if input comes from 
 * an unsanitized source
 * @param {object} el object that will have its property set
 * @param {string} propName ('value', 'style.backgroundColor')
 * Example: setProp(node, 'style.backgroundColor', "#ddd");
 */
function setProp(el, propName, value) {
    var propList = propName.split('.');
    // Note we're not setting it to the last value in the property chain
    for (var i=0; i < propList.length - 1 ; i++) {
        el = el[propList[i]];
    }
    var lastProperty = propList[propList.length -1];
    el[lastProperty] = value;
}

测试用例 使用Firefox访问google.com,在控制台中键入上述代码,然后键入以下内容:

// Set tooltip on links
setListProp( document.getElementsByTagName('a'), 'title', 'YEAH it worked');


// Set bg to red on all links
setListProp( document.getElementsByTagName('a'), 'style.backgroundColor', '#f00');

更新

/** 
 * This exists in many libs and in newer versions of JS on Array's prototype 
 * @param {Object[]} arr The array that we want to act on each element. 
 *                   Does not work for sparse arrays
 * @param {Function} callback The function to be called for each element, it will be passed
 *        the element as its first argument, the index as the secibd
 */
function iterate(arr, callback) {
  for (var i=0,item; item=arr[i]; i++) {
    callback(item, i);
  }
}

你可以这样称呼它

var as = document.getElementsByTagName('a'); 
iterate( as, function(el, index) {
  el.style.backgroundColor = 'red';
  el.innerHTML += "Whatever";
});