function()默认参数中ReferenceError Cannot access ‘a‘ before initialization的解决方法

编程知识更新时间:2023-04-06 10:22:15

function()默认参数中ReferenceError: Cannot access ‘a’ before initialization的解决方法

代码

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<script>
    // 定义一个变量
    let a = 5

    // 写个函数，默认参数
    function f1(a = a) {
        console.log(a)
    }
    // 调用函数
    f1()
</script>
</body>
</html>

报错

test.html?_ijt=11u9c416d56nu6pt74857ikk3a:13 Uncaught ReferenceError: Cannot access 'a' before initialization
    at f1 (test.html?_ijt=11u9c416d56nu6pt74857ikk3a:13:21)
    at test.html?_ijt=11u9c416d56nu6pt74857ikk3a:17:5

原因

function f1(a = a) 中参数a等于 let a ，重新定义了a变量。

解决办法

默认参数：a = a 换成 a1 = a

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<script>
    let a = 5

    function f1(
    // 注意：这里变量名不能是一样的，否则系统认为是重新定义了变量 let a1
    a1 = a
    ) {
        console.log(a)
    }
   
    f1()
</script>
</body>
</html>