javascript - 将字符串收集到 forEach 中的单个数组中

Question

如何在 for Each 循环中将字符串结果收集到单个数组中

<ul>
    <li data-tag="two"></li>
    <li data-tag="three"></li>
    <li data-tag="four"></li>
    <li data-tag="five"></li>
</ul>
<button id="ev">Click</button>

JavaScript:

var elem = Array.prototype.slice.call(document.querySelectorAll('ul > li'));

document.getElementById('ev').addEventListener('click', function(ev){

    elem.forEach( function(el,i) {
        var ar = ["one"];
        var tags = el.getAttribute('data-tag');

        ar.push(tags);
    });

});

结果:

["one", "two"]
["one", "three"]
["one", "four"]
["one", "five"]

期望结果:

["one", "two", "three", "four", "five"]

Answer 1

在forEach之前初始化arr

var elem = Array.prototype.slice.call(document.querySelectorAll('ul > li'));

document.getElementById('ev').addEventListener('click', function(ev) {
    var ar = ["one"];
  
    elem.forEach( function(el,i) {
        var tags = el.getAttribute('data-tag');
        ar.push(tags);
    });
  
    console.log(ar);
});

<ul>
    <li data-tag="two"></li>
    <li data-tag="three"></li>
    <li data-tag="four"></li>
    <li data-tag="five"></li>
</ul>
<button id="ev">Click</button>