Convert String Number To Number In Javascript


Managing data is one of the fundamental concepts of programming. Converting a Number khổng lồ a String is a common và simple operation. The same goes for the other way around, converting a String lớn a number.

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Converting String to Number

As with the previous shown methods, JavaScript also provides functions lớn easily transkhung a String khổng lồ a primitive sầu number. These are parseInt(), parseFloat(), Math.floor(), Math.ceil(), Unary Operator / Multiply by 1.

.parseInt() takes a String as a first argument, và a base khổng lồ which that String will be converted to lớn. This method always returns an integer. .parseFloat() takes a String as an argument, and returns the Float point number equivalent. Math.floor() is used lớn round an integer or floating point number. It returns the nearest integer rounded down. Math.ceil() can be used khổng lồ round an integer or floating point number. Unary Operator By adding a + sign before a String, it will be converted into a number if it follows the right format. Multiply by 1 If a String is multiplied by the primitive number 1, the string will become a number. .parseInt()

The base can be defined by adding prefixes khổng lồ the numbers we want khổng lồ parse:

No prefix - If there isn't a prefix, the radix is 10 (decimal). 0 - If the prefix is 0, then the radix is 8 (octal). Though, this feature is deprecated. 0x - If the prefix is 0x, then the radix is 16 (hexadecimal).

Although, we can simply add an optional argument lớn the method Điện thoại tư vấn, defining the base:

let str = '353'; let fltStr = '353.56'; let binStr = '7'; let nanStr = 'hello'; parseInt(str); // 353 parseInt(fltStr); // 353 parseInt(binStr, 2); // 111 (Binary) parseInt(nanStr); // NaN (Not a Number) .parseFloat() let str = '100'; let fltStr = '100.21'; let nanStr = 'bye'; parseFloat(str); // 353 parseFloat(fltStr); // 353.21 parseFloat(nanStr); // NaN Math.floor()

Surprisingly, this method can also accept Strings, making it yet a way to lớn convert a String lớn an integer.

let str = '100'; let fltStr = '99.89'; let nanStr = 'bye'; Math.floor(str); // 100 Math.floor(fltStr); // 99 Math.floor(nanStr); // NaN Math.ceil()

Very similar to lớn the previous method, Though, this time it returns the nearest integer rounded up.

The method can accept Strings, also making it a way khổng lồ convert a String to a number:

let str = '100'; let fltStr = '100.21'; let nanStr = 'bye'; Math.ceil(str); // 100 Math.ceil(fltStr); // 101 Math.ceil(nanStr); // NaN

Keep in mind that if you're needing to parse floats then both Math.floor and Math.ceil are probably not good options since they'll always convert the strings to the nearest integer equivalent.

Unary Operator

As with Concatenating an Empty String, there is also a workaround that has better performance but lacks readability.

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let str = '100'; let fltStr = '100.21'; let nanStr = 'greetings'; +str // 100 +fltStr // 100.21 +nanStr // NaN +'1000' // 1000 +10.25 // 10.25

While concise và effective, this isn't a very well-known feature of JavaScript, so it's not advised to lớn use since it may make your code not as easy to understvà.

Multiplying by 1

This approach is arguably the faschạy thử one:

let str = '100'; let fltStr = '100.21'; let nanStr = 'greetings'; str * 1; // 100 fltStr * 1; // 100.21 nanStr * 1; // NaN '2000' * 1; // 2000 '102.15' * 1; // 102.15

The previous two approaches work simply due to the fact that JavaScript tries lớn assimilate the data-types used in a statement such as addition or multiplication.

Using String and Number Objects

Another way of transforming a String lớn number or a number to lớn String is creating a new String or Number object with the new keywords.

// Number lớn String let numToStr = new String(2); // String // String lớn Number let strToNum = new Number('2'); // Number

This practice is, however, discouraged. When using primitive sầu data the object methods should not be used to create them. Instantiating a primitive data type with the String or Number class wrapper brings performance and memory issues.


There are many valid ways of manipulating data. It is up lớn the programmer to decide which one they prefer, choosing performance over readability or a balance between the two.

For more information, you can read the following resources:

parseInt parseFloat Math.floor Math.ceil