更改--css - backgroundColor函数（纯javascript）不起作用

Question

有人能告诉我为什么在执行onclick后改变颜色在这里不起作用吗？

function butt(color) {
    if(document.getElementById("bt").style.backgroundColor=="green"){
            document.getElementById("bt").style.backgroundColor="purple";
    }
};
document.getElementById("bt").addEventListener("click", function() {
    butt("green")
});

#bt {
    background-color:yellow;
    border-radius:10%;
    padding:10px;
    margin:20px;
}            

<div class="row">
    <div id="forbutton">
        <button type="button" id="bt">It's me MrButton !</button>
    </div>
</div>

Answer 1

你只是传递字符串＆＃34;绿色＆＃34;通过功能。详情请参阅代码段。

<强>段

＆＃13;

＆＃13;

// pass the string through function
function butt(color) {

  // If string is "green"...
  if (color === "green") {

    // Reference #bt and change it's backgroundColor to purple
    document.getElementById("bt").style.backgroundColor = "purple";
  }

};

// Register #bt to click event, when clicked...
document.getElementById("bt").addEventListener("click", function() {

  // Call butt() function passing the string "green"
  butt("green")
});

＆＃13;

#bt {
  background-color: yellow;
  border-radius: 10%;
  padding: 10px;
  margin: 20px;
}

＆＃13;

<div class="row">
  <div id="forbutton">
    <button id="bt">It's me MrButton !</button>
  </div>

＆＃13;

＆＃13;

＆＃13;