How to add method to String class in JavaScript?
The task is to add a method to the String class in JavaScript. There are two approaches that are described with the proper examples:
Approach 1: Use Object.defineProperty() method, which is used to define a new property directly to an object, or modifies an existing property. It takes 3 arguments, first is Object, Second is propertyName and last is the propertyDescription. In this example, the sum of length of strings is returned.
- Example:
<!DOCTYPE HTML><html><head><title>Add method to String class in JavaScript</title><style>body {text-align: center;}h1 {color: green;}</style></head><body><h1>GeeksforGeeks</h1><pid="GFG_UP"></p><buttononClick="GFG_Fun()">click here</button><pid="GFG_DOWN"></p><script>var up = document.getElementById('GFG_UP');var down = document.getElementById('GFG_DOWN');var str1 = "GeeksforGeeks";var str2 = "A Computer Science Portal";up.innerHTML = "Click on button to get the "+ "sum of length of the both "+ "strings<br>Str1 - '" + str1+ "'<br>Str2 - '" + str2 + "'";Object.defineProperty(String.prototype,'SumOfLength', {value: function(param) {return this.length + param.length;}});function GFG_Fun() {const res = str1.SumOfLength(str2);down.innerHTML = res;}</script></body></html> - Output:
Approach 2: Use String.prototype.propertyName to add a new method to the String class. Define a method which takes arguments passed by the object and perform the desired operation. In this example, sum of length of strings is returned.
- Example:
<!DOCTYPE HTML><html><head><title>Add method to Stringclass in JavaScript</title><style>body {text-align: center;}h1 {color: green;}</style></head><body><h1>GeeksforGeeks</h1><pid="GFG_UP"></p><buttononClick="GFG_Fun()">click here</button><pid="GFG_DOWN"></p><script>var up = document.getElementById('GFG_UP');var down = document.getElementById('GFG_DOWN');var str1 = "GeeksforGeeks";var str2 = "A Computer Science Portal";up.innerHTML = "Click on button to get the "+ "sum of length of the both "+ "strings<br>Str1 - '" + str1+ "'<br>Str2 - '" + str2 + "'";String.prototype.SumOfLength = function( arg ) {return this.length + arg.length;};function GFG_Fun() {const res = str1.SumOfLength(str2);down.innerHTML = res;}</script></body></html> - Output:
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