var array = [
  {100,200},
  {200,200},
  {100,400}
];

if (value in array) {...}

var array = [
  [100,200],
  [200,200],
  [100,400]
];

console.log(array[1][0] == 200 && array[1][1] == 200);

var array = [
    [100,200],
    [200,200],
    [100,400]
];

var searchFor = [200,200];

function arrayExistsInside(haystack, needle) {
    for(var i = 0; i < haystack.length; i++) {
        if(compareArray(haystack[i], needle)) return true;
    }
    return false;
}

function compareArray(array1, array2) {
    if(array1.length != array2.length) return false;

    for(var i = 0; i < array1.length; i++) {
        if(array1[i] != array2[i]) return false;
    }

    return true;
}

if(arrayExistsInside(array, searchFor)) { ... }