There are several ways you can convert JavaScript String to Number. The best way is to make use of the unary plus + operator or the Number global function. You can also make use of the parseint or parsefloat functions. The following examples show how to make use of these functions.
The Unary plus (+) operator converts all string representations of numbers, Boolean values(true and false), and null to numbers. If the operand cannot be converted into a number, the unary plus operator will return NaN
The following are some of the examples
console.log(+"100") //100
console.log(+"100.5175") //100.5175
console.log(+"10AA0.5175") //NaN
console.log(+"") //0
console.log(+" ") //0
console.log(+null) //0
console.log(+undefined) //Nan
console.log(+Infinity) //Infinity
console.log(+true) //1
console.log(+false) //0
console.log(+"0x22") //34
console.log(+"0022") //22
console.log(+"0o51") //41
console.log(+"3.125e7") //31250000
console.log(+"35 35") //NaN
console.log(+"AB 35") //NaN
The parseint function parses an string and returns an integer. The syntax of the parseint is as follows. If you do not provide the radix then it assumes the Hexadecimal number.
parseInt(string, radix)
console.log(parseInt("100")) //100
console.log(parseInt("100.5175")) //100
console.log(parseInt("10AA0.5175")) //10
console.log(parseInt("")) //NaN
console.log(parseInt(null)) //NaN
console.log(parseInt(Infinity)) //NaN
console.log(parseInt(true)) //NaN
console.log(parseInt(false)) //NaN
console.log(parseInt("0x22")) //34
console.log(parseInt("0022")) //22
console.log(parseInt("0o51")) //0
console.log(parseInt("3.125e7")) //3
console.log(parseInt("35 35")) //35
console.log(parseInt("AB 35")) //NaN
You can make use of the radix. The radix can be from 2 to 36. Use span style="color: grey; background-color: powder;"2 for binary,8 for octal, 10 for decimal & 16 for HexaDecimal number.
console.log(parseInt("51")); //51
console.log(parseInt("51",8)); //41
console.log(parseInt("51",16)); //81
console.log(parseInt("051")); //51
console.log(parseInt("051",8)); //41
console.log(parseInt("051",16)); //81
console.log(parseInt("0x51")); //81
console.log(parseInt("0x51",8)); //0
console.log(parseInt("0x51",16)); //81
console.log(parseInt("0o51")); //0
console.log(parseInt("0o51",8)); //0
console.log(parseInt("0o51",16)); //0
ParseFloat is another way to convert string to a number.
console.log(parseFloat("100")) //100
console.log(parseFloat("100.5175")) //100.5175
console.log(parseFloat("10AA0.5175")) //10
console.log(parseFloat("")) //NaN
console.log(parseFloat(null)) //NaN
console.log(parseFloat(Infinity)) //Infinity
console.log(parseFloat(true)) //NaN
console.log(parseFloat(false)) //NaN
console.log(parseFloat("0x22")) //0
console.log(parseFloat("0022")) //22
console.log(parseFloat("0o51")) //0
console.log(parseFloat("3.125e7")) //31250000
console.log(parseFloat("35 35")) //35
console.log(parseFloat("AB 35")) //NaN
You can also use the Number global function. It is very similar to unary plus (+)
console.log(Number("100")) //100
console.log(Number("100.5175")) //100.5175
console.log(Number("10AA0.5175")) //NaN
console.log(Number("")) //0
console.log(Number(" ")) //0
console.log(Number(null)) //0
console.log(Number(undefined)) //Nan
console.log(Number(Infinity)) //Infinity
console.log(Number(true)) //1
console.log(Number(false)) //0
console.log(Number("0x22")) //34
console.log(Number("0022")) //22
console.log(Number("0o51")) //41
console.log(Number("3.125e7")) //31250000
console.log(Number("35 35")) //NaN
console.log(Number("AB 35")) //NaN
The string to number operation may result in a NaN. The NaN stands for not a number. It is the result of numerical operations, where the result is not a number. Hence always check if the value is NaN using the isNaN method after the conversion.
convertToNumber("AB 35")
convertToNumber("35")
function convertToNumber(numVal) {
if (isNaN(+numVal)) {
console.log("Number is NaN")
} else {
console.log(+numVal)
}
}
//Output
Number is NaN
35
