1. Convert Float to Int Using theparseInt() Function in JavaScript
2. Convert Float to Int UsingNumber.toFixed() in JavaScript
3. Convert Float to Int With Bitwise Operators in JavaScript
4. Convert Float to Int UsingMath Library Functions in JavaScript
5. Conclusion

In JavaScript, we have many ways of converting float to int, as shown below.

• TheparseInt() function
• TheNumber.toFixed() method
• Conversion with bitwise operators
  • ApplyingOR by 0
  • Using the doubleNOT operator
  • RightSHIFT by 0
• UsingMath library functions in javascript
  • Math.floor()
  • Math.round()
  • Math.ceil()
  • Math.trunc()

Convert Float to Int Using theparseInt() Function in JavaScript

parseInt() is widely used in JavaScript. With this function, we can convert the values of different data types to the integer type. In this section, we will see the conversion of a float number to an integer number. The syntax ofparseInt() isparseInt(<value>). The following code shows the behavior of the function.

console.log(parseInt(123.321));console.log(parseInt(123.998));

Output:

123123

Remarks

• For more information, refer tothe MSN docs.
• While converting float values,parseInt() discards the decimals and doesn’t consider them while returning the whole number part of the float value.
• parseInt() returnsNaN in case conversion is not possible. Hence, it is good to include anisNaN() check while converting values so that the code is safe and doesn’t break.

Convert Float to Int UsingNumber.toFixed() in JavaScript

Number.toFixed() behaves a bit differently from theparseInt(). It rounds off the number to the nearest integer value. Hence, beware of the rounding fact.Number.toFixed() rounds of the decimal value of float less than.5 to the lower integer value. If the decimal value is0.5 or greater, then the float number will be rounded off to the next higher integer value. The syntax forNumber.toFixed() function is as follows.

numberObject.toFixed(<numberof digits>);

Usually, we need to pass a parameter to this function that specifies the number of digits after the decimal in the output. For our purpose, we need not mention any argument as, by default, it takes the parameter to be0, hence returning an integer value. Refer to the following sample codes.

console.log( (123.123).toFixed(2) );console.log( (123.123).toFixed() );console.log( (123.98).toFixed() );console.log( (123.49).toFixed() );console.log( (123.5).toFixed() );

Output:

123.12123124123124

Remarks

• Unlike theparseInt() method,Number.toFixed() is not that famous for extracting the integer part, as it does a round-up of the float value passed as a parameter.
• One can use this function to convert only float values. Unlike theparseInt() function, string value conversion to float is not supported byNumber.toFixed().

Convert Float to Int With Bitwise Operators in JavaScript

We have seen the methods ofparseInt() and theNumber.toFixed(). Both of these execute some internal operations to get the desired results. The bitwise operators are efficient, fast, and per-formant in converting the float values into an integer when compared to the two methods. We can use the following bitwise operators for the conversion.

ApplyingOR by 0

We can use the bitwiseOR operator to get the whole number part of a floating-point number. The bitwise operators function at the binary level. It converts the operand number to binary, and then the bit by bitOR operation is executed. ApplyingOR with0 to any floating-point number in the acceptable range will return the whole number part of the floating-point value. Refer to the examples below.

console.log(123.321|0);console.log(123.5432|0);console.log(123.921|0);console.log(216|0);console.log(-321.456|0)

Output:

123123123216-321

Using the DoubleNOT Operator

Another bitwise operator is theNOT operator, represented by the~ sign. Being a unary operator, we can use the bitwiseNOT operator to shed off the decimal part in a float number. TheNOT operator, at the binary level, inverts the binary bit values (returning0 for a1 bit and1 for a0 bit value). It means that if a number is represented in binary by10110, then applyingNOT to it gives the inverted value01001. Again applying theNOT functionality returns back the original bits (10110) of the number. Hence, applying theNOT operator twice returns the numeric value, and during the process, it does not change the number if it is an integer. But for a float value, applying theNOT operator twice will return just the whole number part of the float number. The following examples clarify this fact.

console.log(~~(123.321));console.log(~~(123.53));console.log(~~(23.97));console.log(~~(-23.97));console.log(~~(-0.97));

Output:

12312323-230

Right Shift by 0

We can apply the bitwise right shift operator (represented by>> characters). It will convert the float value to an integer. Underneath at the binary level, the bitwise right SHIFT operator shifts the binary bits of the operand to the right by a count specified by the second operand. Hence, it ignores the bits that overflow to the right. In doing so, the function preserves the sign value of the number. The following codes represent the working of the right SHIFT operator.

console.log(123.321>>0);console.log(123.53>>0);console.log(23.97>>0);console.log(-23.97>>0);console.log(-0.97>>0);

Output:

12312323-230

Remarks

• Bitwise operators are faster as it is closest to the machine language and doesn’t need to perform additional check or operations as would be done internally by theparseInt() orNumber.toFixed().
• Bitwise operators like theOR,NOT etc., when applied on large numbers, may give unexpected results. The maximum value supported for getting the decimal value truncated is2147483647 (2³¹-1). Any number more than2147483647 will give unexpected results.
• In JavaScript, floating-point numbers are represented by 64 bits, with one bit reserved for preserving the sign value (positive or negative), 32 bits for the whole number part. The bitwise operators operate on the signed 32-bit numbers ignoring the decimal value. Hence, we get the integer number part of the float value.

Convert Float to Int UsingMath Library Functions in JavaScript

We can use the JavaScriptMath library, which has various functions to get integers from floating-point numbers. Unlike the bitwise operators, these offer additional features based on requirements like rounding off values to the nearest numbers, truncating values, etc. We can use the following methods for this purpose.

Conversion WithMath.floor()

TheMath.floor() function rounds off the value passed as a parameter to the next lower integer value. Syntax ofMath.floor() isMath.floor(<float value>). Following are a few examples that showcase the usage and how it converts a float to a whole number.

console.log(Math.floor(123.321));console.log(Math.floor(123.53));console.log(Math.floor(23.97));console.log(Math.floor(-23.97));console.log(Math.floor(-0.97));

Output:

12312323-24-1

The case of negative float numbers likeMath.floor(-23.97) may seem confusing, but the function rightly converts the value to the next lower integer,-24. Recollect that the higher the numeric value of a negative number, the lesser is its actual value.

Conversion WithMath.round()

Unlike theMath.floor() function,Math.round() approximates the value passed in parameters. If the value after the decimal is5 or greater, then the number is rounded off to the next higher integer. Else, if the value after the decimal is lesser than5, it is rounded to the lower integer. Hence, based on the value post the decimal point,Math.round() function can behave similar toMath.floor() orMath.ceil() functions. Following are a few examples withMath.round().

console.log(Math.round(123.321));console.log(Math.round(123.53));console.log(Math.round(23.97));console.log(Math.round(-23.97));console.log(Math.round(-0.97));

Output:

12312424-24-1

Conversion WithMath.ceil()

TheMath.ceil() function behaves opposite to theMath.floor() function. Instead of rounding off to the next lower integer as inMath.floor(),Math.ceil() returns the next higher integer value. Following are a few conversions withMath.ceil().

console.log(Math.ceil(123.321));console.log(Math.ceil(123.53));console.log(Math.ceil(23.97));console.log(Math.ceil(-23.97));console.log(Math.ceil(-0.97));

Output:

12412424-23-0

Conversion WithMath.trunc()

As the name hints, theMath.trunc() function truncates the decimal value and returns the whole number part of the float value. This method can be considered similar to the bitwise operators discussed earlier. Here, there is no rounding off to the nearest integers. Instead, it returns the whole number part of the float value as it is. Following are a few use cases withMath.trunc().

console.log(Math.trunc(123.321));console.log(Math.trunc(123.53));console.log(Math.trunc(23.97));console.log(Math.trunc(-23.97));console.log(Math.trunc(-0.97));

Output:

12312323-23-0

Conclusion

There are various ways to get the whole number part out of a float value. Bitwise operators are faster in execution as they perform operations on the binary-level without the requirements of conversion or any other processing.parseInt(),Math.trunc() and the bitwise operators (OR by0, DoubleNOT, right shift by0) give the exact whole number as if they tear the float value at the decimal point and return just the whole number part out of it. If we are interested in processing the float number to round it or get the nearest integer based on the business requirement, it would be good to go forNumber.toFixed(),Math.round(),Math.ceil() and theMath.floor() functions.