Syntax error: Illegal return statement in JavaScri

2019-03-22 10:04发布

问题:

I am getting a really weird JavaScript error when I run this code:

<script type = 'text/javascript'>
var ask = confirm('".$message."');
if(ask==false)
{
return false;     
}
else
{
return true;
}
</script>

In the JavaScript console it says:

Syntax Error: Illegal return statement

It occurs at return true; and return false;

(I am echoing this javascript from a php function; the $message variable is one of the php parameters)

What is wrong with my code?

回答1:

return only makes sense inside a function. There is no function in your code.

Also, your code is worthy if the Department of Redundancy Department. Assuming you move it to a proper function, this would be better:

return confirm(".json_encode($message).");

EDIT much much later: Changed code to use json_encode to ensure the message contents don't break just because of an apostrophe in the message.



回答2:

If you want to return some value then wrap your statement in function

function my_function(){ 

 return my_thing; 
}

Problem is with the statement on the 1st line if you are trying to use PHP

var ask = confirm ('".$message."'); 

IF you are trying to use PHP you should use

 var ask = confirm (<?php echo "'".$message."'" ?>); //now message with be the javascript string!!


回答3:

in javascript return statement only used inside function block. if you try to use return statement inside independent if else block it trigger syntax error : Illegal return statement in JavaScript

Here is my example code to avoid such error :

<script type = 'text/javascript'>
(function(){
    var ss= 'no';
    if(getStatus(ss)){
        alert('Status return true');   
    }else{
        alert('Status return false'); 
    }

    function getStatus(ask){
        if(ask=='yes')
        {
        return true;     
        }
        else
        {
        return false;
        }
    }
})();
</script>

Please check Jsfiddle example



回答4:

where are you trying to return the value? to console in dev tools is better for debugging

<script type = 'text/javascript'>
var ask = confirm('".$message."');
function answer(){
  if(ask==false){
    return false;     
  } else {
    return true;
  }
}
console.log("ask : ", ask);
console.log("answer : ", answer());
</script>


回答5:

In my experience, most often this error message means that you have put an accidental closing brace somewhere, leaving the rest of your statements outside the function.

Example:

function a() {
    if (global_block) //syntax error is actually here - missing opening brace
       return;
    } //this unintentionally ends the function

    if (global_somethingelse) {
       //Chrome will show the error occurring here, 
       //but actually the error is in the previous statement
       return; 
    }

    //do something
}