String + JavaScript中的增量值

Question

我在代码中间添加了注释。请帮帮我如果可以，我今天必须交付产品。

 if (a === 3) { //this would be how many of the answers further the action
                 var starting = 2; // for an example: yes or no; two of the answers go to no, one goes to yes. 
                 //                                  we take 2 as a starting point /you can set these individually for each scenario;
                 if (starting === 2) {
                     for (i = 0; i < starting; i++) {
                         answers[i] = 1; //sets the two checking points of the answer to the no, remaining yes;

 document.getElementById("btn" + i).style.backgroundColor = "red";

     // the problem lies here
    // I tried multiple ways but none of them worked so far
    //i want to apply the style change to multiple buttons at once.

                     }

                     alert(answers);

                     for (i = 0; i < starting; i++) {
                         if (answers[i] == 1) {

                         }
                     }

                 }
             }

问题是按钮的名称是btn，按钮的名称是btn1，btn2，btn3;我希望for循环将其更改为所有按钮，但是id的字符串文字不能识别i;

示例：“btn”+ i; =改变btn1的风格

我修好了。错误是for循环从1开始;而且我已经将按钮的ID命名为错误。新手错误！ :)

Answer 1

for (i = 0; i < 3; i++) {
  if (document.getElementById("btn" + i) != undefined)
    document.getElementById("btn" + i).style.backgroundColor = "red";


}

<input type="button" value="Submit" id="btn3">
<input type="button" value="Submit" id="btn1">
<input type="button" value="Submit" id="btn2">

问题是你的按钮id从btn1开始，你的代码从0开始，它不在你的html中，所以要么在设置背景颜色之前添加一个检查，要么从1开始你的循环

if (document.getElementById("btn" + i) != undefined)