use strict Directive

Restricts the use of some features in JavaScript. Supported in Internet Explorer 10 and Windows 8.x Store apps only.

Syntax

use strict  

Remarks

Example

The following code causes a syntax error because in strict mode all variables must be declared with var.

"use strict";  
function testFunction(){  
   var testvar = 4;  
    return testvar;  
}  
intvar = 5;  

See Also

Strict Mode