从两个数组创建/合并对象哈希图

Question

I'm working on a project that requires me to create a hashmap, it's my first one and after researching I am stuck. I need to create the map from two arrays.

Array 1:

var arrayOne = [ "board", "admin" ]

These would be added to a map Object with a default value of false, I can get to this part:

var myMap = {
    board: false,
    admin: false
}

Array 2:

var arrayTwo = [ "board" ]

Only 'board' exists here, so I want to turn the value to 'true'. I'm stuck on where to go next so I end up with:

var myMap = {
    board: true,
    admin: false
}

Here's my script so far:

var myMap = {};
var arrayOne = [ "board", "admin" ];
for (var i = 0; i < arrayOne.length; i++) {
    var a = arrayOne[i];
    myMap[a] = false; // sets default value
}

Any help to do the 'next bit' to merge the two is greatly appreciated, thank you.

Answer 1

I think you should continue with the following:

for (var i = 0; i < arrayTwo.length; i++) {
    if (arrayTwo[i] in myMap)
        myMap[arrayTwo[i]] = true;
}

... setting properties to true only if they exist in the map.

Answer 2

Use indexOf() method to check if the item is in second array or not

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/indexOf

http://www.w3schools.com/jsref/jsref_indexof_array.asp

var myMap = {};
var arrayOne = [ "board", "admin" ];
for (var i = 0; i < arrayOne.length; i++) {
    var a = arrayOne[i];
    myMap[a] = false; // sets default value
    if ( arrayTwo.indexOf( a ) != -1 )
    {
        myMap[a] = true;
    }
}

Answer 3

Just do one then the other...

var i;
var myMap = {};
var arrayOne = [ "board", "admin" ];

for (i = 0; i < arrayOne.length; i++) {
     myMap[arrayOne[i]] = false;
}

var arrayTwo = [ "board" ];

for (i = 0; i < arrayTwo.length; i++) {
     myMap[arrayTwo[i]] = true;
}

Answer 4

ES5 version

arrayOne.forEach(function(item){
    myMap[item] = false;
});
arrayTwo.forEach(function(item){
    (item in myMap) && (myMap[item] = true);
});