JavaScript比较两个数组

Question

Is there i way in JavaScript to compare two arrays;

This is my example.

array1 = ['jpg','png'];

array 2 = ['jpg','pdf','png','bmp'];

I my case i need if are all elements of array1 part of array2 return TRUE, or something. In case only one element of array 1 match, element in array 2 return FALSE. Order its not important. Basciclly this is validation of uploaded files, i try to removing button, if two file are not with right extension.

I try function inarray, but i think it only works with string not array

Answer 1

If legacy is not a problem, Something like this would do:

var array1 = ['jpg','png','d'];
var array2 = ['jpg','pdf','png','bmp'];

var result = !array1.filter(function(a) { return array2.indexOf(a)==-1; }).length;   

// result is False

Answer 2

if are all elements of array1 part of array2 return TRUE
only one element of array1 match, element in array2 return FALSE

You can think about this in two ways,

• take the intersection and check the intersection is the same as the input
• loop over the input and return false on the first mismatch

Here is an example of using a loop

var a = [1, 3],
    b = [1, 5],
    c = [0, 1, 2, 3, 4];

function test(needles, haystack) {
    var i;
    for (i = 0; i < needles.length; ++i) {
        if (haystack.indexOf(needles[i]) === -1) {
            return false;
        }
    }
    return true;
}

test(a, c); // true
test(b, c); // false

Answer 3

If the result of filtering the second array with the values of the first is an array with length equal to the length of the first array, the first array is a subset of the second. You can write a function for that, or assing an extra method to Array.prototype :

 var array1 = ['jpg', 'png']; var array2 = ['jpg', 'pdf', 'png', 'bmp']; var array3 = ['jpg', 'bmp', 'pdf']; Helpers.log2Screen('array1 subset of array2? ', isSubset(array1, array2) ? 'yes' : 'no' ); // assign and use Array.prototype.subsetOf Array.prototype.subsetOf = isSubsetProto; Helpers.log2Screen('array1 subset of array3? ', array1.subsetOf(array3) ? 'yes' : 'no' ); function isSubset(arr1, arr2) { return arr2.filter( function (v) {return arr1.indexOf(v) > -1; } ).length == arr1.length; } function isSubsetProto(arr) { return arr.filter( function (v) {return this.indexOf(v) > -1; }, this ).length == this.length; } 

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