How can I round down a number in Javascript?
Using Math.floor() is one way of doing this.
More information: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/floor
Round towards negative infinity - Math.floor()
+3.5 => +3.0-3.5 => -4.0Round towards zero can be done using Math.trunc(). Older browsers do not support this function. If you need to support these, you can use Math.ceil() for negative numbers and Math.floor() for positive numbers.
+3.5 => +3.0 using Math.floor()-3.5 => -3.0 using Math.ceil()
Math.floor() will work, but it's very slow compared to using a bitwise OR operation:
var rounded = 34.923 | 0;alert( rounded );//alerts "34"EDIT Math.floor() is not slower than using the | operator. Thanks to Jason S for checking my work.
Here's the code I used to test:
var a = [];var time = new Date().getTime();for( i = 0; i < 100000; i++ ) { //a.push( Math.random() * 100000 | 0 ); a.push( Math.floor( Math.random() * 100000 ) );}var elapsed = new Date().getTime() - time;alert( "elapsed time: " + elapsed );