PHP functions on js

PHP.js

function round (value, precision, mode) {	
	var m, f, isHalf, sgn // helper variables
	// making sure precision is integer
	precision |= 0
	m = Math.pow(10, precision)
	value *= m
	// sign of the number
	sgn = (value > 0) | -(value < 0)
	isHalf = value % 1 === 0.5 * sgn
	f = Math.floor(value)

	if (isHalf) {
		switch (mode) {
			case 'PHP_ROUND_HALF_DOWN':
			// rounds .5 toward zero
				value = f + (sgn < 0)
				break
			case 'PHP_ROUND_HALF_EVEN':
			// rouds .5 towards the next even integer
				value = f + (f % 2 * sgn)
				break
			case 'PHP_ROUND_HALF_ODD':
			// rounds .5 towards the next odd integer
				value = f + !(f % 2)
				break
			default:
			// rounds .5 away from zero
				value = f + (sgn > 0)
		}
	}

	return (isHalf ? value : Math.round(value)) / m
}