Convert a string to an integer in JavaScript

In JavaScript parseInt() function is used to convert the string to an integer. This function returns an integer of base which is specified in second argument of parseInt() function.
parseInt() function returns Nan( not a number) when the string doesn’t contain number.

Syntax:

parseInt(Value, radix)

It accepts string as a value and converts it to specified radix system and returns an integer.

Program to convert string to integer:
Example-1:

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<script>
  
    function convertStoI() {
        var a = "100";
        var b = parseInt(a);
        document.write("Integer value is" + b);
        var d = parseInt("3 11 43");
        document.write("</br>");
  
        document.write('Integer value is ' + d);
  
    }
convertStoI(); 
</script>    

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Output:

Integer value is100
Integer value is 3

ParseInt() function converts number which is present in any base to base 10. It parses string and converts until it faces a string literal and stops parsing.

Example-2:

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<script>
  
    function convertStoI() {
        var r = parseInt("1011", 2);
        var k = parseInt("234", 8);
  
        document.write('Integer value is ' + r);
        document.write("<br>");
        document.write("integer value is " + k);
        document.write("<br>");
        document.write(parseInt("528GeeksforGeeks"));
  
    }
convertStoI();
</script>                    

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Output:

Integer value is 11
integer value is 156
528


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