How to check all values of an array are equal or not in JavaScript ?
Given a javaScript array and the task is to print true if all the values of array are same using javaScript.
Approach 1:
- First get the array of elements.
- Pass it to an arrow function, which calls every() method on each array element and return true if each element matches with the first element of the array.
Example 1: This example uses array.every() method to print the desired response.
<!DOCTYPE HTML> <html> <head> <title> Check if all values of array are equal using JavaScript functions </title> </head> <body style = "text-align:center;"> <h1 style = "color:green;" > GeeksForGeeks </h1> <p id = "GFG_UP" style = "font-size: 15px; font-weight: bold;"> </p> <button onclick = "gfg_Run();"> click here </button> <pre id = "GFG_DOWN" style = "color:green; font-size: 20px; font-weight: bold;"> </pre> <script> var el_up = document.getElementById("GFG_UP"); var el_down = document.getElementById("GFG_DOWN"); var arr = [1, 1, 1, 1]; el_up.innerHTML = "Click on button to check if all values are" + " equal<br><br>" + arr; const allEqual = arr => arr.every( v => v === arr[0] ); function gfg_Run() { el_down.innerHTML = allEqual(arr); } </script> </body> </html> |
Output:
- Before clicking on the button:
- After clicking on the button:
Approach 2:
- First get the array of elements.
- Pass it to a function, which calls reduce() method on array element.
- Return true if each element matches with the first element of the array.
Example: This example uses array.reduce() method to print the false for the given array.
<!DOCTYPE HTML> <html> <head> <title> Check if all values of array are equal using JavaScript functions </title> </head> <body style = "text-align:center;"> <h1 style = "color:green;" > GeeksForGeeks </h1> <p id = "GFG_UP" style = "font-size: 15px; font-weight: bold;"> </p> <button onclick = "gfg_Run();"> click here </button> <pre id = "GFG_DOWN" style = "color:green; font-size: 20px; font-weight: bold;"> </pre> <script> var el_up = document.getElementById("GFG_UP"); var el_down = document.getElementById("GFG_DOWN"); var arr = ["GFG", "GFG", "GFG", "GfG"]; el_up.innerHTML = "Click on button to check if all" + " values are equal<br><br>" + arr; function allEqual(arr) { if(!arr.length) return true; return arr.reduce(function(a, b) {return (a === b)?a:(!b);}) === arr[0]; } function gfg_Run() { el_down.innerHTML = allEqual(arr); } </script> </body> </html> |
Output:
- Before clicking on the button:
- After clicking on the button:
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