JavaScript ReferenceError – 左侧赋值无效

ReferenceError 的基本示例 - 左侧分配无效，运行代码并检查控制台

例子：

Javascript

    if (Math.PI = 10 || Math.PI = 5) { 
        document.write("Inside Loop");
    }

输出：

ReferenceError: Invalid left-hand side in assignment

如果代码中的某处分配错误，则会出现此 JavaScript 异常无效分配左侧。单个“=”符号而不是“==”或“===”是无效分配。

信息：

ReferenceError: invalid assignment left-hand side

错误类型：

ReferenceError

错误原因：赋值运算符和比较运算符之间可能存在误解。

例1：在这个例子中，“=”运算符被误用为“==”，所以发生了错误。

HTML

     
    
        
            GeeksforGeeks
        
        
            JavaScript ReferenceError - 
            Invalid assignment left-hand side
        
  
        
            click here
        
        
  
        
            var el_down = document.getElementById("GFG_DOWN");
            function Geeks() {
                try {
                    if ((Math.PI = 10 || Math.PI = 5)) {
                        document.write("Inside Loop");
                    }
                    el_down.innerHTML = 
                      "'Invalid assignment left-hand side'" + 
                      " error has not occurred";
                } catch (e) {
                    el_down.innerHTML = 
                      "'Invalid assignment left-hand side'" + 
                      "error has occurred";
                }
            }
        
    

输出：

例2：在这个例子中， +运算符与声明一起使用，所以错误没有发生。

HTML

  
     
   
 
      
        GeeksforGeeks  
     
    
        JavaScript ReferenceError -
        Invalid assignment left-hand side
    
     
    
        click here
    
     
    
         
     
        var el_down = document.getElementById("GFG_DOWN");
        function Geeks() { 
            try {
                var str = 'Hello, '
                + 'Geeks'; // Error Here
                el_down.innerHTML = 
                "'Invalid assignment left-hand side'"+
                "error has not occurred";
            } catch(e) {
                el_down.innerHTML = 
                "'Invalid assignment left-hand side'"+
                "error has occurred";
            }
        } 
     
   

输出：