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

Question

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

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


        

Answer 1

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

Answer 2

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);
}

Answer 3

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.

Answer 4

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

Answer 5

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.

Answer 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]