What does +_ operator mean in JavaScript?

Unary Operator: A unary operation contain only one operand. Here, ‘+’ unary plus operator converts its operand to Number type. While it also acts as an arithmetic operator with two operands which returns an addition result on calculation.

JavaScript Identifiers: Javascript Identifiers are used to name variables (and keywords, and functions, and labels).In Javascript, the first character must be a letter, or an underscore ( _ ), or a dollar sign ( $ ) but not digit and subsequent characters may be letters, digits, underscores, or dollar signs.

JavaScript +_  operator: It is a combination of the variable with symbol underscore( _ ) and unary plus ( + ) operator, + operator converts the type of _ variable to Number type for further operation.

Example: The variable “_” with string type is stored in variable “r” with “number” type.

  • Input:
    var _ = "1";
    var r = +_;
  • Output:
    typeof(r) will be number

Example 1: Conversion of String to Number



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<!DOCTYPE html>
<html>
    <head>
        <title>Javascript Operator</title>
        <script type="text/javascript"></script>
        <link rel="stylesheet" 
              href="https://www.w3schools.com/w3css/4/w3.css" />
    </head>
    <body>
        <div class="conintainer">
            <p class="w3-jumbo w3-text-green pad" 
               align="center" 
               style="margin: 0 0 0 0;">
              GeeksforGeeks
            </p>
  
            <p class="w3-large w3-text-green pad" 
               align="center">
              A computer science portal for geeks
            </p>
  
            <p align="center">
                Type of variable(_) : 
              <span id="gfg"></span> <br />
                Type of variable(a) : 
              <span id="gfg1"></span>
            </p>
  
            <script type="text/javascript">
                GFG = function (_) {
                    let b = typeof _;
                    let a = +_;
                    let c = typeof a;
  
                    document.getElementById("gfg").innerHTML = b;
                    document.getElementById("gfg1").innerHTML = c;
                };
  
                GFG("21");
            </script>
        </div>
    </body>
</html>

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Output: 

Example 2: Performing arithmetic addition operation by converting them to number type.

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<!DOCTYPE html>
<html>
    <head>
        <title>Addition Operation</title>
        <script type="text/javascript"></script>
        <link rel="stylesheet" 
              href="https://www.w3schools.com/w3css/4/w3.css" />
    </head>
    <body>
        <div class="conintainer">
            <p class="w3-jumbo w3-text-green pad" 
               align="center"
               style="margin: 0 0 0 0;">
              GeeksforGeeks
            </p>
  
            <p class="w3-large w3-text-green pad" 
               align="center">
              A computer science portal for geeks
            </p>
  
            <p align="center">
                Value variable(_) :
              <span id="gfg"></span> <br />
                Value of variable($) :
              <span id="gfg1"></span> <br />
                Value of variable(Sum) :  
              <span id="gfg2"></span>
            </p>
  
            <script type="text/javascript">
                GFG = function (_, $) {
                    let c = +_ + +$;
                    let a = +_;
                    let b = +$;
  
                    document.getElementById("gfg").innerHTML = a;
                    document.getElementById("gfg1").innerHTML = b;
                    document.getElementById("gfg2").innerHTML = c;
                };
  
                GFG("21", "45");
            </script>
        </div>
    </body>
</html>

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Output:

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