In this tutorial, we will learn how to convert a percentage to decimal in JavaScript.
We can use the parseFloat() method to convert the a percentage string '90%' to decimal 0.90
This can be done by creating a function that will take the percentage as input, pass it to the parseFloat(), and then divide the output by 100.
const percentToDecimal = (percentStr) => {
return parseFloat(percentStr) / 100;
};
console.log(percentToDecimal('90%')); //0.9
console.log(percentToDecimal('9%')); //0.09
console.log(percentToDecimal('22.22%')); //0.22219999999999998
parseFloat() takes a string value as input and it will trim everything after the +, -, ., 0-9 characters.
So if the strings start with any of the above, it will trim the characters after them and return the values before it as a number.
console.log(parseFloat("90%")); // 90
Once we have got the number we divide it by 100 to get the decimal value.
console.log(90 / 100); // 0.90
Handling the NaN values while converting percentage to decimal in JavaScript
In case, the string passed to the parseFloat() is starting with different characters it will throw NaN (Not a Number) error.
console.log(parseFloat("%90")); // NaN
To handle that we can add an addition check during the conversion of percent to decimal.
const percentToDecimal = (percentStr) => {
const afterFloatParsing = parseFloat(percentStr);
return isNaN(afterFloatParsing) ? 0 : afterFloatParsing / 100;
};
console.log(percentToDecimal('90%')); // 0.9
console.log(percentToDecimal('9%')); // 0.09
console.log(percentToDecimal('22.22%')); // 0.22219999999999998
console.log(percentToDecimal('%22.22')); // 0
Also see, Format a number to percentage in JavaScript.