# How to convert a string into an integer without using parseInt() function in JavaScript?

The parseInt() is a built-in function in JavaScript that parses a string and returns an integer. However, there are times when we want to convert a string into an integer without using this function. In this article, we'll explore how to do just that.

## Using the unary plus operator

One way to convert a string into an integer is by using the unary plus operator. This operator converts its operand into a number. For instance, the following program converts the string "123" into the number 123 −

### Example 1

<html>
<title>Examples</title>
<body>
<div id="result1"></div>
<div id="result2"></div>
<div id="result3"></div>
<script>
let str = "123";
document.getElementById("result1").innerHTML = typeof str;
let num = +str; // num = 123
document.getElementById("result2").innerHTML = num;
document.getElementById("result3").innerHTML = typeof num;
</script>
</body>
</html>

### Example 2

The unary plus operator can also be used to convert other values into numbers. For example, it can convert booleans into numbers, as shown below −

<html>
<title>Examples</title>
<body>
<div id="result"></div>
<script>
let bool = true;
let num = +bool; // num = 1
document.getElementById("result").innerHTML = num
</script>
</body>
</html>

## Using the Number() function

Another way to convert a string into a number is by using the Number() function. This function takes in an argument and returns a number. For instance, the following code converts the string "123" into the number 123 −

### Example 1

<html>
<title>Examples</title>
<body>
<div id="result1"></div>
<div id="result2"></div>
<div id="result3"></div>
<script>
let str = "123";
document.getElementById("result1").innerHTML = typeof str;
let num = Number(str); // num = 123
document.getElementById("result2").innerHTML = num;
document.getElementById("result3").innerHTML = typeof num;
</script>
</body>
</html>

### Example 2

The Number() function can also be used to convert other values into numbers. For example, it can convert booleans into numbers, as shown below −

<html>
<title>Examples</title>
<body>
<div id="result"></div>
<script>
let bool = false;
let num = Number(bool); // num = 1
document.getElementById("result").innerHTML = num
</script>
</body>
</html>

## Using the Math.floor() function

The Math.floor() function returns the largest integer less than or equal to a given number. This function can be used to convert a string into an integer.

### Example

The following code converts the string "123" into the number 123 −

<html>
<title>Examples</title>
<body>
<div id="result1"></div>
<div id="result2"></div>
<div id="result3"></div>
<script>
let str = "123";
document.getElementById("result1").innerHTML = typeof str;
let num = Math.floor(str); // num = 123
document.getElementById("result2").innerHTML = num;
document.getElementById("result3").innerHTML = typeof num;
</script>
</body>
</html>

In the above code, we first convert the string "123" into a number using the Number() function. We then pass this number into the Math.floor() function, which returns the integer 123.

## Using the bitwise operators

Bitwise operators are operators that perform operations on bitwise values. These operators can be used to convert a string into an integer.

### Example

The following code converts the string "765" into the number 765 −

<html>
<title>Examples</title>
<body>
<div id="result1"></div>
<div id="result2"></div>
<div id="result3"></div>
<script>
let str = "765";
document.getElementById("result1").innerHTML = typeof str;
let num = str|0;
document.getElementById("result2").innerHTML = num;
document.getElementById("result3").innerHTML = typeof num;
</script>
</body>
</html>

In the above code, we use the bitwise OR operator (|) to convert the string "765" into a number. The bitwise OR operator converts its operands into 32-bit integers and then performs a bitwise OR operation on them. In this case, it converts the string "765" into the number 765.

## Using the Math.ceil() function

The Math.ceil() function returns the smallest integer greater than or equal to a given number. This function can be used to convert a string into an integer.

### Example

The following code converts the string "123" into the number 123 −

<!doctype html>
<html>
<title>Examples</title>
<body>
<div id='result1'></div>
<div id='result2'></div>
<div id='result3'></div>
<script>
let str = '123';
document.getElementById('result1').innerHTML ="String:" +str;
document.getElementById('result2').innerHTML = "Before:<br> Type: "+typeof str;
let num = Math.ceil(str); // num = 123
document.getElementById('result3').innerHTML = "After:<br> Type:"+typeof num;
</script>
</body>
</html>

In the above code, we first convert the string "123" into a number using the Number() function. We then pass this number into the Math.ceil() function, which returns the integer 123.

There are a few ways to convert a string into an integer without using the parseInt() function. These include using the unary plus operator, the Number() function, the Math.floor() function, and the bitwise operators.