In this post, we will quickly go through String() and Number() functions in JavaScript.


1. String()


Both the following ways of defining a string in JavaScript are same.


var str = "Hello World";
console.log(str); //Hello World


var Str = new String("Hello World");
console.log(Str.toString()); //Hello World


toUpperCase() and toLowerCase() methods of String() object.


var Str = new String("Hello World");
console.log(typeof Str); //Object
console.log(Str.toUpperCase()); //HELLO WORLD
console.log(Str.toLowerCase()); //hello world


charAt() return the character at the specified position. inedxOf() returns the index of a particular character. You can specify a second argument to indexOf() that would start reading the string from that character.


console.log(Str.charAt(4)); //"o"
console.log(Str.charAt(12)); // returns nothing as char does not exists at index 12
console.log(Str.indexOf('o')); //4
console.log(Str.indexOf('o', 5)) //7


slice(arg1, arg2) method will return a substring of the string. The substring starts from arg1 index of the string and ends at arg2-1 index of the string.


split(arg) will convert the string to an array. The argument specified in split will act as separator.


var Str = new String("Hello World-this-is a great world");

console.log(Str.slice(1,4)); //ell
console.log(Str.split(' ')); //[ "Hello", "World-this-is", "a", "great", "world" ]
console.log(Str.split('-')); //[ "Hello World", "this", "is a great world" ]



2. Number()


Two similar ways of getting the same result. One is direct, another one is by using constructor function.


var num = 12;
console.log(num); //12
var Num = new Number('12');
console.log(Num.valueOf()); //12


Some standard properties of Number() functions are as follows:




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