JavaScript | RegExp ?! Quantifier

The RegExp ?!m Quantifier in JavaScript is used to find the match of any string which is not followed by a specific string m.

Syntax:

/?!m/ 

or

new RegExp("?!m")

Syntax with modifiers:

/\?!m/g 

or

new RegExp("?!m", "g")

Example 1: This example matches the words ‘Geeks’ not followed by 123 in the whole string.

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<!DOCTYPE html>
<html>
  
<head>
    <title>
        JavaScript RegExp ?! Quantifier
    </title>
</head>
  
<body style="text-align:center">
      
    <h1 style="color:green">GeeksforGeeks</h1>
      
    <h2>RegExp ?! Quantifier</h2>
      
    <p>Input String: Geeksfor123\nGeeks@</p>
      
    <button onclick="geek()">Click it!</button>
      
    <p id="app"></p>
      
    <script>
        function geek() {
            var str1 = "Geeks for 123 Geeks@";
            var regex4 = /Geeks(?!123)/g;
            var match4 = str1.match(regex4);
  
            document.getElementById("app").innerHTML
                    = "Found " + match4.length
                    + " matches: " + match4;
        }
    </script>
</body>
  
</html>                    

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Output:
Before Clicking the button:
ques1
After Clicking the button:
ques1

Example 2: This example replaces the word ‘128’ with ‘#’.

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<!DOCTYPE html>
<html>
  
<head>
    <title>
        JavaScript RegExp ?! Quantifier
    </title>
</head>
  
<body style="text-align:center">
      
    <h1 style="color:green">GeeksforGeeks</h1>
      
    <h2>RegExp ?! Quantifier</h2>
      
    <p>String: @128Geek128</p>
      
    <button onclick="geek()">Click it!</button>
      
    <p id="app"></p>
      
    <script>
        function geek() {
            var str1 = "@128Geek128";
            var regex4 = new RegExp("128(?!ee)", "gi");         
            var replace = "#";
            var match4 = str1.replace(regex4, replace);
            document.getElementById("app").innerHTML = 
                " New string: " + match4;
        }
    </script>
</body>
  
</html>                    

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Output:
Before Clicking the button:
ques1
After Clicking the button:
ques1

Supported Browsers: The browsers supported by RegExp ?! Quantifier are listed below:

  • Google Chrome
  • Apple Safari
  • Mozilla Firefox
  • Opera
  • Internet Explorer


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