var intvalue = Math.floor( floatvalue );
var intvalue = Math.ceil( floatvalue );
var intvalue = Math.round( floatvalue );
// `Math.trunc` was added in ECMAScript 6
var intvalue = Math.trunc( floatvalue );
Math object reference
Examples
Positive// value=x // x=5 5<x<5.5 5.5<=x<6
Math.floor(value) // 5 5 5
Math.ceil(value) // 5 6 6
Math.round(value) // 5 5 6
Math.trunc(value) // 5 5 5
parseInt(value) // 5 5 5
~~value // 5 5 5
value | 0 // 5 5 5
value >> 0 // 5 5 5
value >>> 0 // 5 5 5
value - value % 1 // 5 5 5
// value=x // x=-5 -5>x>=-5.5 -5.5>x>-6
Math.floor(value) // -5 -6 -6
Math.ceil(value) // -5 -5 -5
Math.round(value) // -5 -5 -6
Math.trunc(value) // -5 -5 -5
parseInt(value) // -5 -5 -5
value | 0 // -5 -5 -5
~~value // -5 -5 -5
value >> 0 // -5 -5 -5
value >>> 0 // 4294967291 4294967291 4294967291
value - value % 1 // -5 -5 -5
// x = Number.MAX_SAFE_INTEGER/10 // =900719925474099.1
// value=x x=900719925474099 x=900719925474099.4 x=900719925474099.5
Math.floor(value) // 900719925474099 900719925474099 900719925474099
Math.ceil(value) // 900719925474099 900719925474100 900719925474100
Math.round(value) // 900719925474099 900719925474099 900719925474100
Math.trunc(value) // 900719925474099 900719925474099 900719925474099
parseInt(value) // 900719925474099 900719925474099 900719925474099
value | 0 // 858993459 858993459 858993459
~~value // 858993459 858993459 858993459
value >> 0 // 858993459 858993459 858993459
value >>> 0 // 858993459 858993459 858993459
value - value % 1 // 900719925474099 900719925474099 900719925474099
// x = Number.MAX_SAFE_INTEGER/10 * -1 // -900719925474099.1
// value = x // x=-900719925474099 x=-900719925474099.5 x=-900719925474099.6
Math.floor(value) // -900719925474099 -900719925474100 -900719925474100
Math.ceil(value) // -900719925474099 -900719925474099 -900719925474099
Math.round(value) // -900719925474099 -900719925474099 -900719925474100
Math.trunc(value) // -900719925474099 -900719925474099 -900719925474099
parseInt(value) // -900719925474099 -900719925474099 -900719925474099
value | 0 // -858993459 -858993459 -858993459
~~value // -858993459 -858993459 -858993459
value >> 0 // -858993459 -858993459 -858993459
value >>> 0 // 3435973837 3435973837 3435973837
value - value % 1 // -900719925474099 -900719925474099 -900719925474099
Top answer 1 of 16
2261
var intvalue = Math.floor( floatvalue );
var intvalue = Math.ceil( floatvalue );
var intvalue = Math.round( floatvalue );
// `Math.trunc` was added in ECMAScript 6
var intvalue = Math.trunc( floatvalue );
Math object reference
Examples
Positive// value=x // x=5 5<x<5.5 5.5<=x<6
Math.floor(value) // 5 5 5
Math.ceil(value) // 5 6 6
Math.round(value) // 5 5 6
Math.trunc(value) // 5 5 5
parseInt(value) // 5 5 5
~~value // 5 5 5
value | 0 // 5 5 5
value >> 0 // 5 5 5
value >>> 0 // 5 5 5
value - value % 1 // 5 5 5
// value=x // x=-5 -5>x>=-5.5 -5.5>x>-6
Math.floor(value) // -5 -6 -6
Math.ceil(value) // -5 -5 -5
Math.round(value) // -5 -5 -6
Math.trunc(value) // -5 -5 -5
parseInt(value) // -5 -5 -5
value | 0 // -5 -5 -5
~~value // -5 -5 -5
value >> 0 // -5 -5 -5
value >>> 0 // 4294967291 4294967291 4294967291
value - value % 1 // -5 -5 -5
// x = Number.MAX_SAFE_INTEGER/10 // =900719925474099.1
// value=x x=900719925474099 x=900719925474099.4 x=900719925474099.5
Math.floor(value) // 900719925474099 900719925474099 900719925474099
Math.ceil(value) // 900719925474099 900719925474100 900719925474100
Math.round(value) // 900719925474099 900719925474099 900719925474100
Math.trunc(value) // 900719925474099 900719925474099 900719925474099
parseInt(value) // 900719925474099 900719925474099 900719925474099
value | 0 // 858993459 858993459 858993459
~~value // 858993459 858993459 858993459
value >> 0 // 858993459 858993459 858993459
value >>> 0 // 858993459 858993459 858993459
value - value % 1 // 900719925474099 900719925474099 900719925474099
// x = Number.MAX_SAFE_INTEGER/10 * -1 // -900719925474099.1
// value = x // x=-900719925474099 x=-900719925474099.5 x=-900719925474099.6
Math.floor(value) // -900719925474099 -900719925474100 -900719925474100
Math.ceil(value) // -900719925474099 -900719925474099 -900719925474099
Math.round(value) // -900719925474099 -900719925474099 -900719925474100
Math.trunc(value) // -900719925474099 -900719925474099 -900719925474099
parseInt(value) // -900719925474099 -900719925474099 -900719925474099
value | 0 // -858993459 -858993459 -858993459
~~value // -858993459 -858993459 -858993459
value >> 0 // -858993459 -858993459 -858993459
value >>> 0 // 3435973837 3435973837 3435973837
value - value % 1 // -900719925474099 -900719925474099 -900719925474099
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348
Bitwise OR operator
A bitwise or operator can be used to truncate floating point figures and it works for positives as well as negatives:
function float2int (value) {
return value | 0;
}
Results
float2int(3.1) == 3
float2int(-3.1) == -3
float2int(3.9) == 3
float2int(-3.9) == -3
Performance comparison?
I've created a JSPerf test that compares performance between:
Math.floor(val)val | 0bitwise OR~~valbitwise NOTparseInt(val)
that only works with positive numbers. In this case you're safe to use bitwise operations well as Math.floor function.
But if you need your code to work with positives as well as negatives, then a bitwise operation is the fastest (OR being the preferred one). This other JSPerf test compares the same where it's pretty obvious that because of the additional sign checking Math is now the slowest of the four.
Note
As stated in comments, BITWISE operators operate on signed 32bit integers, therefore large numbers will be converted, example:
1234567890 | 0 => 1234567890
12345678901 | 0 => -539222987
W3Schools
w3schools.com › js › js_number_methods.asp
JavaScript Number Methods
The valueOf() method is used internally in JavaScript to convert Number objects to primitive values.
Videos
MDN Web Docs
developer.mozilla.org › en-US › docs › Web › JavaScript › Reference › Global_Objects › Number
Number - JavaScript | MDN
A number literal like 37 in JavaScript code is a floating-point value, not an integer. There is no separate integer type in common everyday use. (JavaScript also has a BigInt type, but it's not designed to replace Number for everyday uses.
MDN Web Docs
developer.mozilla.org › en-US › docs › Web › JavaScript › Reference › Global_Objects › Number › isInteger
Number.isInteger() - JavaScript | MDN
The Number.isInteger() static method determines whether the passed value is an integer. function fits(x, y) { if (Number.isInteger(y / x)) { return "Fits!"; } return "Does NOT fit!"; } console.log(fits(5, 10)); // Expected output: "Fits!" console.log(fits(5, 11)); // Expected output: "Does NOT fit!"
MDN Web Docs
developer.mozilla.org › en-US › docs › Web › JavaScript › Reference › Global_Objects › Number › parseInt
Number.parseInt() - JavaScript | MDN
The Number.parseInt() static method parses a string argument and returns an integer of the specified radix or base. function roughScale(x, base) { const parsed = Number.parseInt(x, base); if (Number.isNaN(parsed)) { return 0; } return parsed * 100; } console.log(roughScale(" 0xF", 16)); // ...
GeeksforGeeks
geeksforgeeks.org › javascript › how-to-convert-a-float-number-to-the-whole-number-in-javascript
How to Convert a Float Number to the Whole Number in JavaScript? - GeeksforGeeks
July 11, 2025 - Below are various methods to convert float numbers to whole numbers in JavaScript: ... Round off the number passed as a parameter to its nearest integer in the Downward direction.
Top answer 1 of 16
3114
The simplest way would be to use the native Number function:
var x = Number("1000")
If that doesn't work for you, then there are the parseInt, unary plus, parseFloat with floor, and Math.round methods.
parseInt()
var x = parseInt("1000", 10); // You want to use radix 10
// So you get a decimal number even with a leading 0 and an old browser ([IE8, Firefox 20, Chrome 22 and older][1])
Unary plus
If your string is already in the form of an integer:
var x = +"1000";
floor()
If your string is or might be a float and you want an integer:
var x = Math.floor("1000.01"); // floor() automatically converts string to number
Or, if you're going to be using Math.floor several times:
var floor = Math.floor;
var x = floor("1000.01");
parseFloat()
If you're the type who forgets to put the radix in when you call parseInt, you can use parseFloat and round it however you like. Here I use floor.
var floor = Math.floor;
var x = floor(parseFloat("1000.01"));
round()
Interestingly, Math.round (like Math.floor) will do a string to number conversion, so if you want the number rounded (or if you have an integer in the string), this is a great way, maybe my favorite:
var round = Math.round;
var x = round("1000"); // Equivalent to round("1000", 0)
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306
Try parseInt function:
var number = parseInt("10");
But there is a problem. If you try to convert "010" using parseInt function, it detects as octal number, and will return number 8. So, you need to specify a radix (from 2 to 36). In this case base 10.
parseInt(string, radix)
Example:
var result = parseInt("010", 10) == 10; // Returns true
var result = parseInt("010") == 10; // Returns false
Note that parseInt ignores bad data after parsing anything valid.
This guid will parse as 51:
var result = parseInt('51e3daf6-b521-446a-9f5b-a1bb4d8bac36', 10) == 51; // Returns true
MDN Web Docs
developer.mozilla.org › en-US › docs › Web › JavaScript › Reference › Global_Objects › parseInt
parseInt() - JavaScript | MDN
The parseInt() function parses a string argument and returns an integer of the specified radix (the base in mathematical numeral systems).
W3Schools
w3schools.com › jsref › jsref_parseint.asp
JavaScript parseInt() Method
The parseInt method parses a value as a string and returns the first integer. A radix parameter specifies the number system to use: 2 = binary, 8 = octal, 10 = decimal, 16 = hexadecimal. If radix is omitted, JavaScript assumes radix 10.
Go Make Things
gomakethings.com › converting-strings-to-numbers-with-vanilla-javascript
Converting strings to numbers with vanilla JavaScript | Go Make Things
Today, let’s look at three different ways to convert a string into a number. The parseInt() method converts a string into an integer (a whole number).
Educative
educative.io › answers › how-to-convert-string-to-int-or-number-in-javascript
How to convert string to int or number in JavaScript
Use Number() or the unary + operator if you want to handle both integers and floats automatically. These methods are useful when you need to convert directly to a number regardless of the format of the input string.
GeeksforGeeks
geeksforgeeks.org › javascript › convert-a-string-to-an-integer-in-javascript
Convert a String to an Integer in JavaScript - GeeksforGeeks
July 11, 2025 - The number() method converts a string into an integer number. It works similarly to the unary plus operator.
Vultr Docs
docs.vultr.com › javascript › global › parseInt
JavaScript parseInt() - Parse String to Integer | Vultr Docs
September 30, 2024 - Use parseInt() to convert the string to an integer. ... This code converts the string "123" into the integer 123. It's a straightforward example of how parseInt() interprets and converts string data.
TutorialsPoint
tutorialspoint.com › how-to-convert-a-string-into-integer-in-javascript
How to convert a string into integer in JavaScript?
In this approach to convert string to integer in JavaScript, we have used Math.trunc method. It returns the integer part of the number by truncating the decimal digits.
freeCodeCamp
freecodecamp.org › news › how-to-convert-a-string-to-a-number-in-javascript
How to Convert a String to a Number in JavaScript
May 2, 2022 - Another method would be to subtract 0 from the string. Like before, JavaScript is converting our string value to a number and then performing that mathematical operation. ... The bitwise NOT operator (~) will invert the bits of an operand and ...
TechOnTheNet
techonthenet.com › js › number_parseint.php
JavaScript: Number parseInt() method
In JavaScript, parseInt() is a Number method that is used to parse a string and return its value as an integer number.
Bacancy Technology
bacancytechnology.com › qanda › javascript › convert-string-to-integer-in-javascript
How to Convert String to Integer in JavaScript
August 5, 2025 - In JavaScript, you can convert a string to an integer using the following methods: let str = "123"; let num = parseInt(str); console.log(num); // 123 · let str = "123"; let num = +str; console.log(num); // 123 · let str = "123"; let num = Number(str); console.log(num); // 123 ·
Built In
builtin.com › articles › javascript-string-to-a-number
How to Convert a JavaScript String to Number | Built In
Below are several different methods you can use to convert a string into a number in JavaScript with example code. parseInt() parses a string and returns a whole number. Spaces are allowed. Only the first number is returned. This method has a limitation though. If you parse the decimal number, it will be rounded off to the nearest integer value and that value is converted to string.
JavaScript.info
javascript.info › tutorial › the javascript language › data types
Numbers
They “read” a number from a string until they can’t. In case of an error, the gathered number is returned. The function parseInt returns an integer, whilst parseFloat will return a floating-point number:
Simplilearn
simplilearn.com › home › resources › software development › javascript tutorial: learn javascript from scratch › a guide to convert string to int in javascript
Convert String to an Int (Integer) in JavaScript | Simplilearn
September 16, 2025 - Learn how to convert string to an Int or Integer in JavaScript with correct syntax. Understand how to use the parseInt() method and find out examples for reference.
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