Different ways to convert string to number in JavaScript
In this article, We will see different ways to convert string type values to numbers.
1. parseInt()
This method accepts a string parameter and converts it into an integer type value. If passed input value in not convertable to number then it returns NaN.
Case 1: If the input value is number
let str1 = '123';
console.log(parseInt(str1)); // Output: 123
Case 2: If the input value is a combination of number and non-number characters.
let str2 = '123xyz';
console.log(parseInt(str2)); // Output: 123
Case 3: If the input value is a combination of number and non-number characters.
let str3 = 'xyz123';
console.log(parseInt(str3)); // Output: NaN
Case 4: If the input is emptry string
let str4 = '';
console.log(parseInt(str4)); // Output: NaN
Case 5: If the input is string with decimal value in it
let str5 = '11.5';
console.log(parseInt(str5)); // Output: 11
2. parseFloat()
This method accepts a string parameter and converts it into a floating point type value. If the passed input value is not Convertable to a number then it returns NaN.
Case 1: If the input value is number
let str1 = '123';
console.log(parseFloat(str1)); // Output: 123
Case 2: If the input value is a combination of number and non-number characters.
let str2 = '123xyz';
console.log(parseFloat(str2)); // Output: 123
Case 3: If the input value is a combination of number and non-number characters.
let str3 = 'xyz123';
console.log(parseFloat(str3)); // Output: NaN
Case 4: If the input is emptry string
let str4 = '';
console.log(parseFloat(str4)); // Output: NaN
3. Number()
The function accepts a string parameter and converts it to an integer or floating point number. If the passed input value is not Convertable to a number then it returns NaN.
Case 1: If the input value is number
let str1 = '123';
console.log(Number(str1)); // Output: 123
Case 2: If the input value is a combination of number and non-number characters.
let str2 = '123xyz';
console.log(Number(str2)); // Output: NaN
Case 3: If the input value is a combination of number and non-number characters.
let str3 = 'xyz123';
console.log(Number(str3)); // Output: NaN
Case 4: If the input is emptry string
let str4 = '';
console.log(Number(str4)); // Output: 0
4. Using Unary Operator (+)
In this approach, The unary plus operator (+) is placed before a string value which converts it to an integer or floating point number. If the passed input value is not Convertable to a number then it returns NaN.
Case 1: If the input value is number
let str1 = '123';
console.log(+str1); // Output: 123
Case 2: If the input value is a combination of number and non-number characters.
let str2 = '123xyz';
console.log(+str2); // Output: NaN
Case 3: If the input value is a combination of number and non-number characters.
let str3 = 'xyz123';
console.log(+str3); // Output: NaN
Case 4: If the input is emptry string
let str4 = '';
console.log(+str4); // Output: 0
5. Multiply by 1 (*1)
It works similar the above approach.
Syntax:
let str1 = '123';
console.log(str1*1); // Output: 123
6. Math.floor()
Like others, This method also accepts a string parameter and converts it into an integer that is rounded down to the lowest whole number. If passed input value in not Convertable to a number then it returns NaN.
Case 1: If the input value is number
let str1 = '123';
console.log(Math.floor(str1)); // Output: 123
Case 2: If the input value is a combination of number and non-number characters.
let str2 = '123xyz';
console.log(Math.floor(str2)); // Output: NaN
Case 3: If the input value is a combination of number and non-number characters.
let str3 = 'xyz123';
console.log(Math.floor(str3)); // Output: NaN
Case 4: If the input is emptry string
let str4 = '';
console.log(Math.floor(str4)); // Output: 0
Case 5: If the input is decimal value
let str5 = '11.7';
console.log(Math.floor(str5)); // Output: 11
7. Math.round()
Case 1: If the input value is number
let str1 = '123';
console.log(Math.round(str1)); // Output: 123
Case 2: If the input value is a combination of number and non-number characters.
let str2 = '123xyz';
console.log(Math.round(str2)); // Output: NaN
Case 3: If the input value is a combination of number and non-number characters.
let str3 = 'xyz123';
console.log(Math.round(str3)); // Output: NaN
Case 4: If the input is emptry string
let str4 = '';
console.log(Math.round(str4)); // Output: 0
Case 5: If the input is decimal value
let str5 = '11.7';
console.log(Math.round(str5)); // Output: 12, Because passed value is closest to 12
Case 6: If the input is decimal value
let str5 = '11.4';
console.log(Math.round(str5)); // Output: 11, Because passed value is closest to 11
8. Using double tilde (~~) Operator
Case 1: If the input value is number
let str1 = '123';
console.log(~~str1); // Output: 123
Case 2: If the input value is a combination of number and non-number characters.
let str2 = '123xyz';
console.log(~~str2); // Output: 0
Case 3: If the input value is a combination of number and non-number characters.
let str3 = 'xyz123';
console.log(~~str3); // Output: 0
Case 4: If the input is emptry string
let str4 = '';
console.log(~~str4); // Output: 0
Case 5: If the input is string(with decimal value in it)
let str5 = '11.4';
console.log(~~str5); // Output: 11
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