You could take a Set and filter the array by a check if the value exists or not.

• If exist reject the element.

• If not, add the value to the set and take the element.

var array = [["apple", "ghana", 15], ["apple", "brazil", 16], ["orange", "nigeria", 10], ["banana", "ghana", 6]],
    seen = new Set,
    result = array.filter(([value]) => !seen.has(value) && seen.add(value));

console.log(result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

If you need compatibility to older browsers, since .filter() is supported only by IE9 you can also loop through the elements of the array(or write the implementation of filter, provided by MDN).

var item = [];
for (var i = 0; i < collection.length; i++) {
    var coll = collection[i];
    if (coll[0] == sourceId && coll[1] == targetId) item.push(coll);
}

you can use below code

var arr = [[1,2], [1,2], [1,3], [1,4], [1,4], [1,4]]; 
var uniqueArrays = []; 
var theCount = [];
var test = [], obj ={};
arr.forEach(val => {
    if(test.indexOf(val.toString()) == -1){
        test.push(val.toString());
        obj[val.toString()] = 1;
        uniqueArrays.push(val);
    }else{
        obj[val.toString()] += 1;

    }

})
theCount = Object.values(obj);
console.log(uniqueArrays);
console.log(theCount);

Hope it will help you.

You have to loop two (or three times):

1. Loop through all "rows", from beginning to the end

2. Loop again, through all "rows", from beginning to the end

   • If the lists are equal, ignore it
   • Otherwise,

3. Loop through all "columns":

   • If the values are not equal, jump to the parent loop.
   • After the loop, remove the element using the .splice method.

Demo: http://jsfiddle.net/EuEHc/

Code:

for (var i=0; i<items.length; i++) {
    var listI = items[i];
    loopJ: for (var j=0; j<items.length; j++) {
        var listJ = items[j];
        if (listI === listJ) continue; //Ignore itself
        for (var k=listJ.length; k>=0; k--) {
            if (listJ[k] !== listI[k]) continue loopJ;
        }
        // At this point, their values are equal.
        items.splice(j, 1);
    }
}

Or for those looking for a one-liner (simple and functional) compatible with current browsers:

let a = ["1", "1", "2", "3", "3", "1"];
let unique = a.filter((item, i, ar) => ar.indexOf(item) === i);
console.log(unique);

Update 2021 I would recommend checking out Charles Clayton's answer, as of recent changes to JS there are even more concise ways to do this.

Update 18-04-2017

It appears as though 'Array.prototype.includes' now has widespread support in the latest versions of the mainline browsers (compatibility)

Update 29-07-2015:

There are plans in the works for browsers to support a standardized 'Array.prototype.includes' method, which although does not directly answer this question; is often related.

Usage:

["1", "1", "2", "3", "3", "1"].includes("2");     // true

Pollyfill (browser support, source from mozilla):

// https://tc39.github.io/ecma262/#sec-array.prototype.includes
if (!Array.prototype.includes) {
  Object.defineProperty(Array.prototype, 'includes', {
    value: function(searchElement, fromIndex) {

      // 1. Let O be ? ToObject(this value).
      if (this == null) {
        throw new TypeError('"this" is null or not defined');
      }

      var o = Object(this);

      // 2. Let len be ? ToLength(? Get(O, "length")).
      var len = o.length >>> 0;

      // 3. If len is 0, return false.
      if (len === 0) {
        return false;
      }

      // 4. Let n be ? ToInteger(fromIndex).
      //    (If fromIndex is undefined, this step produces the value 0.)
      var n = fromIndex | 0;

      // 5. If n ≥ 0, then
      //  a. Let k be n.
      // 6. Else n < 0,
      //  a. Let k be len + n.
      //  b. If k < 0, let k be 0.
      var k = Math.max(n >= 0 ? n : len - Math.abs(n), 0);

      // 7. Repeat, while k < len
      while (k < len) {
        // a. Let elementK be the result of ? Get(O, ! ToString(k)).
        // b. If SameValueZero(searchElement, elementK) is true, return true.
        // c. Increase k by 1.
        // NOTE: === provides the correct "SameValueZero" comparison needed here.
        if (o[k] === searchElement) {
          return true;
        }
        k++;
      }

      // 8. Return false
      return false;
    }
  });
}

This requires JavaScript 1.7:

var arr = [[7,3], [7,3], [3,8], [7,3], [7,3], [1,2]];

arr.map(JSON.stringify).filter((e,i,a) => i === a.indexOf(e)).map(JSON.parse)
// [[7,3], [3,8], [1,2]]

Credit goes to jsN00b for shortest version.