需要为横幅添加三个clickTag,其名称类似于clickTag1,clickTag2,clickTag3。现在代码看起来像这样:
for(var i = 1; i <= 3; i++) {
document.getElementById('Destination_cta_' + i).addEventListener('click', function() {
window.open(clickTag2, '_blank'); //here I want clickTag look like clickTag + i, but its not working.
})
}
所以问题是如何循环var名称,所以我不需要像现在一样手动放置它。
答案 0 :(得分:1)
您想为此使用数组。数组是一个索引的值列表。
var clickTags = ["","www.nba.com","www.nhl.com","www.nfl.com"];
for(var i = 1; i <= 3; i++) {
document.getElementById('Destination_cta_' + i).addEventListener('click', function() {
window.open(clickTags[i], '_blank'); //here I want clickTag look like clickTag + i, but its not working.
})
}
注意,因为您在1
而不是0
开始循环,所以我为clickTags
数组的索引0添加了一个空白条目。
答案 1 :(得分:1)
解决此问题的最简单方法是使用Array。
[, clickTag1, clickTag2, clickTag3].forEach(function(e, i) {
document.getElementById('Destination_cta_' + i).addEventListener('click', function() {
window.open(e, '_blank');
})
})
另一种方法:如果clickTag
是全局变量,则可以始终将它们作为window
对象的全局属性进行访问:
for(var i = 1; i <= 3; i++) (function (i) {
document.getElementById('Destination_cta_' + i).addEventListener('click', function() {
window.open(window['clickTag' + i], '_blank')
})
)(i)
附加包装功能修复了上面评论中提到的闭包错误。
答案 2 :(得分:1)
for (var i = 1; i <= 3; i++) {
// During your first loop there is a local variable `i` whose value is 1
document.getElementById('Destination_cta_' + i)
// Here you pass an anonymous function as the second argument to addEventListener
// This creates a closure, which means the function's context includes variables
// that were in scope when it was created. Right now we have the `for` loop's variable
// `i` in the current scope, so the function keeps a *reference* to that variable.
.addEventListener('click', function() {
// When this get executed in the future, the function has to know about the variable `i`,
// and thankfully there is a reference to it in this function's closure. But remember that
// the for loop executed 3 times, using that same variable. That means that every function
// was created with a closure that is keeping a reference to the same variable, whose final
// value after the loop finished, was 4.
window.alert('clickTag' + i); // Will always alert 'clickTag4' no matter which is clicked
})
}
&#13;
<div id="Destination_cta_1">1</div>
<div id="Destination_cta_2">2</div>
<div id="Destination_cta_3">3</div>
&#13;
确保每个addEventListener
调用在其自己的闭包中获得具有正确值的函数。这样做的方法是使用一个立即调用的函数表达式,传递给你想要的值:
for (var i = 1; i <= 3; i++) {
var element = document.getElementById('Destination_cta_' + i)
element.addEventListener('click', (function(index) {
// This function is now a closure with a reference to index
return function() {
window.alert('clickTag' + index);
}
})(i)) // calling the anonymous function with the current value of `i` binds that value
// to the function's scope
}
&#13;
<div id="Destination_cta_1">1</div>
<div id="Destination_cta_2">2</div>
<div id="Destination_cta_3">3</div>
&#13;