javascript tutorial - [Solved-5 Solutions] How to perform integer division and get the remainder we javascript ? - javascript - java script - javascript array



Problem:

In JavaScript, how do we get:

  • the whole number of times a given integer goes into another?
  • the remainder?

Solution 1:

For some number y and some divisor x compute the quotient (quotient) and remainder (remainder) as:

var quotient = Math.floor(y/x);
var remainder = y % x;
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Solution 2:

I'm no expert in bitwise operators, but here's another way to get the whole number:

var num = ~~(a / b);
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This seems correct as well:

var num = (a / b) >> 0;
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Solution 3:

We did some speed tests on Firefox.

-100/3             // -33.33..., 0.3663 millisec
Math.floor(-100/3) // -34,       0.5016 millisec
~~(-100/3)         // -33,       0.3619 millisec
(-100/3>>0)        // -33,       0.3632 millisec
(-100/3|0)         // -33,       0.3856 millisec
(-100-(-100%3))/3  // -33,       0.3591 millisec

/* a=-100, b=3 */
a/b                // -33.33..., 0.4863 millisec
Math.floor(a/b)    // -34,       0.6019 millisec
~~(a/b)            // -33,       0.5148 millisec
(a/b>>0)           // -33,       0.5048 millisec
(a/b|0)            // -33,       0.5078 millisec
(a-(a%b))/b        // -33,       0.6649 millisec
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The above is based on 10 million trials for each

Conclusion: Use (a/b>>0) (or (~~(a/b)) or (a/b|0)) to achieve about 20% gain in efficiency. Also keep in mind that they are all inconsistent with Math.floor, when a/b<0 && a%b!=0.

Solution 4:

ES6 introduces the new Math.trunc method.

var div = Math.trunc(y/x);
var rem = y % x;
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Note that Math methods have the advantage over bitwise operators that they work with numbers over 231.

Solution 5:

	var remainder = x % y;
return (x - remainder) / y;
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