comparing two arrays before adding an item from one array to another in JavaScript [closed]

Answer 1

You could use Array#some() and stop the iteration if one item is not in the addTo array.

var addFrom = ["orange", "banana", "watermelon", "lemon", "peach"],
    addTo = ["pear", "tangerine", "grape", "orange", "blueberry"];

addFrom.some(function (a) {
    if (!~addTo.indexOf(a)) {
        addTo.push(a);
        return true;
    }
});

document.write('
 ' + JSON.stringify(addTo, 0, 4) + '
');