jquery - getting the index of the similar values of 2 arrays

Question

I want to get the indices of the similar values of array1 and array2 and store it to the stored_index variable.

array1 = ["50","51","52","53","54","55","56","57","58","59"];

array2 = ["59","55","51"];

The stored index should look like this.

stored_index = [9,5,1]; // index 9,5,1 is equal to their indices in array 1

Answer 1

Javascript map() can do this:

var array1 = ["50","51","52","53","54","55","56","57","58","59"];
var array2 = ["59","55","51"];
var stored_index = array2.map(function(val){
    return array1.indexOf(val)
}).filter(function(val){
    return (val != -1)
});

console.log(stored_index)

DEMO

---

Removing filter:

var array1 = ["50","51","52","53","54","55","56","57","58","59"];
var array2 = ["59","55","51"];
var stored_index = array2.map(function(val){
    return (array1.indexOf(val) != -1) ? array1.indexOf(val) : null;
});

console.log(stored_index)//output [9, 5, 1]

Updated DEMO

Answer 2

Try to use Array.prototype.map() along with Array.prototype.indexOf() to achieve what you want,

var array1 = ["50","51","52","53","54","55","56","57","58","59"];
var array2 = ["59","55","51"];
var stored_index = array2.map(function(val){
  return array1.indexOf(val);
});

DEMO

Answer 3

Just loop through array 2 and use IndexOf function

var array1 = ["50","51","52","53","54","55","56","57","58","59"];
var array2 = ["59","55","51"];
var output = [];
for(var item in array2){
  output.push(array1.indexOf(array2[item]));
}

Answer 4

If by any chance you need both the index list and the intersection you could store the intersection in a3 array then index it.

var array1 = ["50", "51", "52", "53", "54", "55", "56", "57", "58", "59"];
var array2 = ["59", "55", "51"];
var a3 = array1.filter(function (n) {
    return array2.indexOf(n) !== -1
});

alert(a3);
stored_index = [];
var i = 0;
for (; i < a3.length; i++) {
    stored_index.push(array1.indexOf(a3[i]));
}
alert(stored_index);

NOTE: for VERY large arrays performance might not be optimal here.

Answer 5

Further to the existing answers, I'd suggest:

var array1 = ["50", "51", "52", "53", "54", "55", "56", "57", "58", "59"],
    array2 = ["59", "55", "51"];

// named function, to which arguments are passed:    
function getIndicesOfCommonArrayValues(one, two) {

    // if the named arguments both match the
    // assessment within the Array.prototype.every()
    // anonymous function we proceed, otherwise we
    // do nothing; if every assessment performed
    // returns true, then the method itself returns
    // a Boolean true:
    if ([one, two].every(function (arr) {
        // 'arr' is the current array-value of the array
        // over which we're iterating:

        // here check that the typeof arr is not 'undefined', AND
        // that the constructor of arr is Array; this ensures that
        // we have two defined array-values, and that the array
        // value we're testing is itself an Array:
        return 'undefined' !== typeof arr && arr.constructor === Array;
    })) {

        // here we find the longest array:
        var longestArray = one.length >= two.length ? one : two,
        // here we find the shortest array:
            shortestArray = one.length < two.length ? one : two;

        // we return the array returned by Array.prototype.map(),
        // which iterates over the shortest array:
        return shortestArray.map(function (value) {
            // 'value' is the current array-value of 
            // the array over which we're iterating.

            // if the longestArray contains the current
            // array-value:
            if (longestArray.indexOf(value) > -1) {

                // we return the index of that array
                // value to the array we're creating
                // Array.prototype.map():
                return longestArray.indexOf(value);
            }
        });
    }
}

console.log(getIndicesOfCommonArrayValues(array1, array2));

var array1 = ["50", "51", "52", "53", "54", "55", "56", "57", "58", "59"],
    array2 = ["59", "55", "51"];

function getIndicesOfCommonArrayValues(one, two) {
    if ([one, two].every(function (arr) {
        return 'undefined' !== typeof arr && arr.constructor === Array;
    })) {
        var longestArray = one.length >= two.length ? one : two,
            shortestArray = one.length < two.length ? one : two;
        
        return shortestArray.map(function (value) {
            if (longestArray.indexOf(value) > -1) {
                return longestArray.indexOf(value);
            }
        });
    }
}

console.log(getIndicesOfCommonArrayValues(array1, array2));

External JS Fiddle demo for experimentation and development.

References:

• Array.prototype.every().
• Array.prototype.indexOf().
• Array.prototype.map().
• Object.prototype.constructor.