When working with data in JavaScript, it is common to encounter situations where a string needs to be converted to an integer. This operation is fundamental as it allows for easier mathematical calculations and comparisons. Fortunately, JavaScript offers several methods to convert strings to integers.
In this article, we will explore the various methods of converting strings to integers in JavaScript, including the parseInt() function, unary plus operator, and the Number() function. We will also highlight the differences between the methods and demonstrate their use with code examples.
 The parseInt() function
The parseInt() function is a builtin function in JavaScript that converts strings to integers. It takes two arguments: the string to be converted and the radix. The radix is optional, and its default value is 10.
The function works by parsing the string from left to right and stopping when it encounters a nondigit character. The parsed integer is then returned. If the first character of the string cannot be converted to a number, the function returns NaN (Not a Number).
Here's an example of using the parseInt() function:
let strNum = "42";
let intNum = parseInt(strNum);
console.log(intNum); // Output: 42
In this example, strNum is a string that represents the number 42. The parseInt() function takes this string and converts it to an integer, which is then stored in the intNum variable. The output of the console.log() function is the integer value 42.
Here's another example that demonstrates the use of the radix argument:
let strHex = "0xff";
let intHex = parseInt(strHex, 16);
console.log(intHex); // Output: 255
In this example, we use the radix argument to specify that the string represents a hexadecimal value. The output of the console.log() function is the integer value 255.
 The unary plus operator
The unary plus operator (+) is another method of converting strings to integers in JavaScript. It works by placing the + operator before the string to be converted. If the string can be converted to a number, the result is an integer value. If the string cannot be converted to a number, the result is NaN.
Here's an example of using the unary plus operator:
let strNum = "42";
let intNum = +strNum;
console.log(intNum); // Output: 42
In this example, we use the unary plus operator to convert the string "42" to the integer value 42. The output of the console.log() function is the integer value 42.
Here's another example that demonstrates the use of the unary plus operator with a nonnumeric string:
let strNaN = "hello";
let intNaN = +strNaN;
console.log(intNaN); // Output: NaN
In this example, we use the unary plus operator to convert the string "hello" to a number, which results in NaN. The output of the console.log() function is NaN.
 The Number() function
The Number() function is another builtin function in JavaScript that can be used to convert strings to integers. It works by taking a string as its argument and returning a numeric value. If the string cannot be converted to a number, the result is NaN.
Here's an example of using the Number() function:
let strNum = "42";
let intNum = Number(strNum);
console.log(intNum); // Output: 42
In this example, we use the Number() function to convert the string "42" to the integer value 42. The output of the console.log() function is the integer value 42.
Here's another example that demonstrates the use of the Number() function with a nonnumeric string:
let strNaN = "hello";
let intNaN = Number(strNaN);
console.log(intNaN); // Output: NaN
In this example, we use the Number() function to convert the string "hello" to a number, which results in NaN. The output of the console.log() function is NaN.
Conclusion
In conclusion, there are several methods to convert strings to integers in JavaScript. The most commonly used methods are the parseInt() function, unary plus operator, and the Number() function. The choice of the method to use depends on the specific requirements of the code being developed.
The parseInt() function is ideal for converting a string to an integer with a specified radix. The unary plus operator is useful for simple conversions but can be less readable in some cases. The Number() function is the most flexible method, capable of handling a wide range of numeric inputs.
In any case, it is always important to ensure that the input string can be safely converted to a number. This can be done by using regular expressions or other validation techniques to check for invalid characters.
Hopefully, this article has helped you understand the different methods of converting strings to integers in JavaScript. We encourage you to experiment with these methods to find the best solution for your specific use case.
let's dive a bit deeper into some of the concepts we covered earlier.
 The parseInt() function
The parseInt() function is a powerful tool for converting strings to integers, but it has some quirks that can be surprising. One important thing to note is that if the first character of the string can't be converted to a number, parseInt() will return NaN, even if the rest of the string can be parsed into an integer. For example:
let strNum = "42abc";
let intNum = parseInt(strNum);
console.log(intNum); // Output: 42
In this example, the string "42abc" starts with the number 42, but also includes nonnumeric characters. When we use parseInt() to convert this string to an integer, it ignores the "abc" and returns the number 42. However, if the string doesn't start with a number, parseInt() will always return NaN:
let strNum = "hello42";
let intNum = parseInt(strNum);
console.log(intNum); // Output: NaN
In this example, the string "hello42" doesn't start with a number, so parseInt() can't parse it into an integer. As a result, it returns NaN.
Another quirk of parseInt() is that it can also interpret strings in other radixes (i.e. bases), not just base 10. For example:
let strHex = "0xff";
let intHex = parseInt(strHex, 16);
console.log(intHex); // Output: 255
In this example, we use the parseInt() function to convert the hexadecimal string "0xff" to an integer. We specify a radix of 16, which tells parseInt() to interpret the string as a hexadecimal number. The output of the console.log() function is the integer value 255.
 The unary plus operator
The unary plus operator is a simple and concise way to convert a string to a number, but it can be less readable than other methods. It's important to note that the unary plus operator only works if the entire string can be parsed into a number. If the string contains nonnumeric characters, the result will be NaN:
let strNum = "42";
let intNum = +strNum;
console.log(intNum); // Output: 42
let strMixed = "42abc";
let intMixed = +strMixed;
console.log(intMixed); // Output: NaN
In this example, we use the unary plus operator to convert two strings to numbers. The first example works correctly because the entire string can be parsed into a number. The second example returns NaN because the string "42abc" can't be fully parsed into a number.
One advantage of using the unary plus operator is that it can sometimes be faster than other methods, particularly when converting single values. However, as with all performance optimizations, it's important to test the actual performance in your specific use case.
 The Number() function
The Number() function is a flexible method for converting strings to numbers, as it can handle a wide range of inputs. However, it has some surprising behavior when dealing with certain types of strings. One important thing to note is that the Number() function will return NaN when trying to parse infinity or negative infinity:
let strInfinity = "Infinity";
let numInfinity = Number(strInfinity);
console.log(numInfinity); // Output: Infinity
let strNegInfinity = "Infinity";
let numNegInfinity = Number(strNegInfinity);
console.log(numNegInfinity); // Output: Infinity
let strNaN = "NaN";
let numNaN = Number(strNaN);
console.log(numNaN); // Output: NaN
In this example, we use the Number() function to parse three different strings that represent special numeric values: "Infinity", "Infinity", and "NaN". The output of the console.log() function shows that "Infinity" and "Infinity" are correctly parsed into their respective values, but "NaN" returns NaN.
Another quirk of the Number() function is that it will return NaN when parsing strings with leading or trailing whitespace:
let strWhitespace = " 42 ";
let numWhitespace = Number(strWhitespace);
console.log(numWhitespace); // Output: 42
let strNonNumericWhitespace = " hello ";
let numNonNumericWhitespace = Number(strNonNumericWhitespace);
console.log(numNonNumericWhitespace); // Output: NaN
In this example, we use the Number() function to parse two different strings that include leading and trailing whitespace. The string " 42 " is correctly parsed into the number 42, but the string " hello " returns NaN because it can't be parsed into a number.
Overall, each of these methods has its strengths and weaknesses, and the best choice depends on the specific requirements of your code. It's important to understand the quirks and limitations of each method to avoid unexpected behavior in your application.
Popular questions

What is the parseInt() function in JavaScript?
A: The parseInt() function is a builtin function in JavaScript that converts strings to integers. It takes a string as input and returns an integer. 
How does the unary plus operator convert a string to an integer?
A: The unary plus operator (+) is a simple method of converting a string to an integer. It works by placing the + operator before the string to be converted. If the string can be converted to a number, the result is an integer value. If the string cannot be converted to a number, the result is NaN. 
What is the Number() function in JavaScript?
A: The Number() function is a builtin function in JavaScript that converts a string to a numeric value. It works by taking a string as its argument and returning a numeric value. If the string cannot be converted to a number, the result is NaN. 
How can you specify a radix when using the parseInt() function?
A: The parseInt() function can interpret strings in various radixes, not just base 10. To specify a radix, you can pass a second argument to the function, which represents the radix to use. If no radix is specified, the default is base 10. 
What can happen if the string being converted to an integer contains nonnumeric characters?
A: If the string being converted to an integer contains nonnumeric characters, the resulting value will be NaN. This can happen with all three methods discussed in this article: parseInt(), unary plus operator, and Number() function.
Tag
Parsing