The String prototype property is used to pad a number with leading zeros. This property allows for adding new properties and methods to existing object types.
Syntax:
object.prototype.name = value
Return value: It returns a reference to the String.prototype object.
Example 1: This example adds leading zeros to a number by creating a function and inside this function, if the number is less than the width provided then it adds the leading zeros.
<!DOCTYPE html> < html > < head > < title > JavaScript | Pad a number with leading zeros </ title > </ head > < body style = "text-align:center;" id = "body" > < h1 style = "color:green;" > GeeksForGeeks </ h1 > < p id = "GFG_UP" style = "font-size: 16px;" ></ p > < button onclick = "gfg_Run()" > click here </ button > < p id = "GFG_DOWN" style = "color:green; font-size: 20px; font-weight: bold;"> </ p > < script > var el_up = document.getElementById("GFG_UP"); var el_down = document.getElementById("GFG_DOWN"); var num = 2213; el_up.innerHTML = 'Number = ' +num; function pad(n, width) { n = n + ''; return n.length >= width ? n : new Array(width - n.length + 1).join('0') + n; } function gfg_Run() { el_down.innerHTML = pad(num, 7); } </ script > </ body > </ html > |
Output:
- Before clicking on the button:
- After clicking on the button:
Example 2: This example adds leading zeros to a number by creating a prototype pad. In this example we can pass a string to the object, whatever we want to pad with the number.
<!DOCTYPE html> < html > < head > < title > JavaScript | Pad a number with leading zeros </ title > </ head > < body style = "text-align:center;" id = "body" > < h1 style = "color:green;" > GeeksForGeeks </ h1 > < p id = "GFG_UP" style = "font-size: 16px;" ></ p > < button onclick = "gfg_Run()" > click here </ button > < p id = "GFG_DOWN" style = "color:green; font-size: 20px; font-weight: bold;"> </ p > < script > var el_up = document.getElementById("GFG_UP"); var el_down = document.getElementById("GFG_DOWN"); var num = '29213'; el_up.innerHTML = 'Number = ' + num; String.prototype.pad = function(String, len) { var str = this; while (str.length < len ) str = String + str; return str; } function gfg_Run() { el_down.innerHTML = num .pad("0", 9); } </script> </ body > </ html > |
Output:
- Before clicking on the button:
- After clicking on the button: