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JavaScript - what is the difference between let and var?

1 points
Created by:
AnnLen
9180

1. Main differences between let and var keywords are:

  • let keyword varialbes do not have varialble hoisting.
    variable hoisting is shifting varialbe declarations to top of source code making them accessible above.

    Example 1:
    <!doctype html>
    <html>
    <body>
      <script>
    
        'use strict';
    
        a = 2; // variable hosting allows for assigning before declaration
        console.log(a);
    
        var a;
    
      </script>
    </body>
    </html>

    Output:

    2


    Example 2:

    <!doctype html>
    <html>
    <body>
      <script>
    
        'use strict';
    
        var a = 2;
        console.log(a);
    
      </script>
    </body>
    </html>

    Output:

    2

     

  • let keyword varialbes can be created in different scopes:
      let keyword variables var keyword variables
    global scope yes yes
    function scope yes yes
    curly braces scope yes no

2. Tips

  • ALWAYS use let keyword.

See also

  1. What is scope in JavaScript?

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