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Accepted
filicaliva
Asked:2020-04-03 23:51:49 +0000 UTC2020-04-03 23:51:49 +0000 UTC

addeventlistener 输出问题

  • 772

问题在于之后的所有内容的输出。

let button = document.querySelectorAll(".number"),
    clear = document.getElementById("clear"),
    textview = document.getElementById("textview"),
    result = document.getElementById("result"),
    del = document.getElementById("delete");

for( let b in button ){
button[b].addEventListener("click", function(){
    return textview.value += button[b].value;
});}    // output data

clear.addEventListener("click", function(){
     return textview.value = " ";
});     //clear

result.addEventListener("click", function(){
     return textview.value = eval(textview.value);
});     //result

del.addEventListener("click", function(){
    return textview.value = (textview.value).slice(0, -1);
});
javascript

1 个回答

  1. Best Answer

    querySelectorAll返回的不是一个数组，而是一个类似数组的对象。

    不正确：

    let button = document.querySelectorAll(".number");
for( let b in button ){
  console.log(b);
}
    <div class="number"></div>
<div class="number"></div>

    正确：

    let button = document.querySelectorAll(".number");
for(let b = 0; b < button.length; b++){
  console.log(b);
}
    <div class="number"></div>
<div class="number"></div>

    或者

    document.querySelectorAll(".number").forEach((el, b) => console.log(b));
    <div class="number"></div>
<div class="number"></div>

    • 2

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