How To Convert string to number in Angular/Typescript

To convert string to number in angular or typescript follow the below steps.

1. Check if a string is number or not using Number() function.
2. If the string is number then convert Number() returns the numeric value or NaN (Not a Number).

We will take a sample typescript string and convert it to number.

var stringToConvert = "759";
var numberValue = Number(stringToConvert);
console.log(numberValue);
//Returns 759

var stringToConvert = "A123";
var numberValue = Number(stringToConvert);
console.log(numberValue);
//Returns NaN

It’s better to check if the string is NaN before converting it to a number.

We will use isNaN() typescript function to check if a string is NaN.

var stringToConvert = "A123";

if(!isNaN(Number(stringToConvert))){
  var numberValue = Number(stringToConvert);
} else{
    console.log('Not a Number');
}

Now we will write a function to convert string to number in our angular project.

function ConvertStringToNumber(input: string) {
    var numeric = Number(input);
    return numeric;
}

ConvertStringToNumber('124'); //124
ConvertStringToNumber('080909'); //80909
ConvertStringToNumber('A345');//NaN
ConvertStringToNumber('-1908');//-1908
ConvertStringToNumber('');//0
ConvertStringToNumber('   ');//0

Typescript’s Number() method returns 0,if the string is empty or contain whitespces.

To handle this scenario we will first check if the string is empty or not

function ConvertStringToNumber(input: string) { 
    if (input.trim().length==0) { 
        return NaN;
    }
    return Number(input);
}

Now the above method return NaN incase if the string is empty or contain white spaces.

Instead of using Number() function we can use unary plus operator to convert string to number.

+'1278'; //1278
+'asfa34'; //NaN

If typescript compiler --stringNullCheck option is disabled we can assign null values to strings. In that case Number(null) returns 0.

To handle this case we will add a null check condition for our above ConvertToNumber() method

function ConvertStringToNumber(input: string) { 
    
    if (!input) return NaN;

    if (input.trim().length==0) { 
        return NaN;
    }
    return Number(input);
}