For what it's worth, for most practical purposes, `arr.sort((a, b) => b - a))` works well enough. (The only thing it doesn't work well with are NaNs, but in practice, those almost never occur.)
On Tue, Jun 27, 2017, 16:11 森建 <[email protected]> wrote: > PHP, Ruby, Groovy have spaceship operator `<=>`. In short, this operator > compares values and returns `1`, `-1`, `0`. > > ECMAScript spec's `TypedArray#sort` has the default comparison part like > following code, so I think it's useful that appending spaceship operator to > ECMAScript like it. > > http://www.ecma-international.org/ecma-262/8.0/#sec-%typedarray%.prototype.sort > > ```javascript > function isPlusZero(val) { > return val === 0 && 1 / val === Infinity; > } > > function defaultCompare(x, y) { > const [isNaN_x, isNaN_y] = [Number.isNaN(x), Number.isNaN(y)]; > > if(isNaN_x && isNaN_y) > return 0; > > if(isNaN_x) > return 1; > > if(isNaN_y) > return -1; > > if(x < y) > return -1; > > if(x > y) > return 1; > > if(x === 0 && y === 0) { > const [isPlusZero_x, isPlusZero_y] = [isPlusZero(x), > isPlusZero(y)]; > > if(!isPlusZero_x && isPlusZero_y) > return -1; > > if(isPlusZero_x && !isPlusZero_y) > return 1; > } > > return 0; > } > ``` > > ```javascript > // NaN behave like the biggest number > NaN <=> NaN // 0 > NaN <=> 42 // 1 > 42 <=> NaN // -1 > Infinity <=> NaN // -1 > > // finite > 10 <=> 10 // 0 > -1 <=> 10 // -1 > 10 <=> -1 // 1 > > // 0, -0 are not the same > -0 <=> 0 // -1 > 0 <=> -0 // 1 > ``` > > ## Use cases > > ```javascript > // Array#sort can use TypedArray#sort default comparison part > [10, 5, NaN, -1].sort((a, b) => a <=> b); // [-1, 5, 10, NaN] > > // desc order > new Float64Array([10, 5, NaN, -1]).sort((a, b) => -(a <=> b)); // [NaN, > 10, 5, -1] > ``` > > ## Problems > > `TypedArray#sort` default comparison part has no `string` order function. > > ```javascript > "abc" <=> "def" // same as "abc".localeCompare("def") ? > "abc" <=> 42 // same as "abc".localeCompare("42") ? > ``` > > I found the reference to spaceship operator in ES Discuss. It has Already > discussed in TC39 meeting? > https://esdiscuss.org/topic/informative-notes#content-3 > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss >
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