New feature isNumber & improve type checking for @turf/helpers fixes #914

[DenisCarriere]

New feature isNumber & improve type checking for @turf/helpers

• add isNumber feature to @turf/helpers
• Improve Number type checking for helper methods:
  • point
  • lineString
  • polygon
• Added isNumber to @turf/turf

Ref: #914
CC: @stebogit @markmeyerphoto

[stebogit]

👍 @DenisCarriere

[stebogit]

@DenisCarriere maybe you could add a comment to briefly explain why this test only on the first coords, or just a reference to the issue. It might seem odd otherwise for somebody who looks at the code for the first time, don't you think?

[stebogit]

Why don't we check a single random coordinate per ring instead of just the first one? That way we would introduce a slightly better check with more or less the same effort. No?
Like (not tested):

var randomRing = Math.floor(Math.random() * coordinates.length);
for (var i = 0; i < coordinates.length; i++) {
    var randomCoord = Math.floor(Math.random() * ring.length);
    for (var j = 0; j < ring[ring.length - 1].length; j++) {
        if (i === randomRing && j === randomCoord && !isNumber(ring[randomCoord][0]) || !isNumber(ring[randomCoord][1])) throw new Error('Coordinates must contain numbers');
        ...
    }
}

(naming too long, but just to give an idea)

[DenisCarriere]

🤔 Good train of thought, however testing the first point would be plenty, this would most likely catch 99% of all typing errors, this type of type check validation shouldn't even be included since this type of error is already being caught in the Typescript definition as Position[][].

As for benchmark performance, simply adding isNumber is a 2x speed reduction, introducing a Math.random + Math.floor would slow things down even more.

Doing 1 point validation should be plenty enough to catch those silly errors.

[DenisCarriere]

maybe you could add a comment to briefly explain why this test only on the first coords

👍 yep sounds good

[DenisCarriere]

@stebogit Actually the Math.random + Math.floor didn't slow things down as much as I thought:

// Using isNumber + Random Point selection
polygon x 5,305,908 ops/sec ±0.99% (87 runs sampled)
// Only using isNumber
polygon x 6,006,338 ops/sec ±1.07% (86 runs sampled)
// No number Type checking
polygon x 11,742,649 ops/sec ±0.83% (90 runs sampled)