underscore.js - Determine if all values in an array of arrays match

问题

I have an array of arrays, which looks something like this:

[["Some string", "Some other string"],["Some third string", "some fourth string"]]

I think I can use the _.all method in Underscore to determine if all of the arrays match 100% (that is all of their values match), but I'm not sure how to write the required iterator to run the check.

Anyone have an idea?

回答1:

Try this guy (order-independent):

function allArraysAlike(arrays) {
  return _.all(arrays, function(array) {
    return array.length == arrays[0].length && _.difference(array, arrays[0]).length == 0;
  });
}

This is assuming you want all of the arrays to contain all the same elements ~~in the same order~~ as one another (so for your example input the function should return false).

回答2:

Why not intersection? (if you really want to use some Underscore functions for this) http://underscorejs.org/#intersection

If the arrays are of the same length, and the length of the intersection equals to the length of the arrays, then they all contain the same values.

回答3:

My preference:

_.isEqual(_.sortBy(first), _.sortBy(second))

And if order matters:

_(first).isEqual(second)

回答4:

Use underscore to determine the difference between the two, and check the length of the array. An easy way to do this would be:

_.isEmpty(_.difference(array1, array2)) && _.isEmpty(_.difference(array2, array1))

This will return true if they are the same and false if they are not.

回答5:

_.isEmpty(_.xor(array1, array2))

回答6:

If you want to check that the elements are the same and in the same order, I would go with:

arrayEq = function(a, b) {
  return _.all(_.zip(a, b), function(x) {
    return x[0] === x[1];
  });
};

Even more neatly in coffeescript:

arrayEq = (a,b) ->
    _.all _.zip(a,b), (x) -> x[0]==x[1]

回答7:

My implementation with http://underscorejs.org/

/**
 * Returns true if the arrays are equal
 *
 * @param {Array} array1
 * @param {Array} array2
 * @returns {boolean}
 */
equal: function ( array1, array2 )
{
    return ( array1.length === array2.length)
        && (array1.length === _.intersection( array1, array2 ).length);
}

回答8:

If you don't need to know which elements are unequal, use transitivity:

function allEqual(list) {
  return _.all(list.slice(1), _.partial(_.isEqual, list[0]));
}
allEqual([2, 2, 2, 2]) //=> true
allEqual([2, 2, 3, 2]) //=> false
allEqual([false])      //=> true
allEqual([])           //=> true

回答9:

I can't comment on Dan Tao's answer, small change to skip checking of first array against itself (unnecessary _.difference call)

function allArraysAlike(arrays) {
    return _.all(arrays, function(array) {
        if(array === arrays[0]) return true;
        return array.length == arrays[0].length && _.difference(array, arrays[0]).length == 0;
    });
}

来源：https://stackoverflow.com/questions/10110510/underscore-js-determine-if-all-values-in-an-array-of-arrays-match

标签

javascript

underscore.js