JavaScript dictionary with names

Question

I want to create a dictionary in JavaScript like the following:

myMappings = [
    { "Name": 10%},
    { "Phone": 10%},
    { "Addres         


        

Answer 1

An object technically is a dictionary.

var myMappings = {
    mykey1: 'myValue',
    mykey2: 'myValue'
};

var myVal = myMappings['myKey1'];

alert(myVal); // myValue

You can even loop through one.

for(var key in myMappings) {
    var myVal = myMappings[key];
    alert(myVal);
}

There is no reason whatsoever to reinvent the wheel. And of course, assignment goes like:

myMappings['mykey3'] = 'my value';

And ContainsKey:

if (myMappings.hasOwnProperty('myKey3')) {
    alert('key already exists!');
}

I suggest you follow this: http://javascriptissexy.com/how-to-learn-javascript-properly/

Answer 2

I suggest not using an array unless you have multiple objects to consider. There isn't anything wrong this statement:

var myMappings = {
    "Name": 0.1,
    "Phone": 0.1,
    "Address": 0.5,
    "Zip": 0.1,
    "Comments": 0.2
};

for (var col in myMappings) {
    alert((myMappings[col] * 100) + "%");
}

Answer 3

You may be trying to use a JSON object:

var myMappings = { "name": "10%", "phone": "10%", "address": "50%", etc.. }

To access:

myMappings.name;
myMappings.phone;
etc..

Answer 4

Another approach would be to have an array of objects, with each individual object holding the properties of a column. This slightly changes the structure of "myMappings", but makes it easy to work with:

var myMappings = [
    { title: "Name", width: "10%" },
    { title: "Phone", width: "10%" },
    { title: "Address", width: "50%" },
    { title: "Zip", width: "10%" },
    { title: "Comments", width: "20%" }
];

Then you could easily iterate through all your "columns" with a for loop:

for (var i = 0; i < myMappings.length; i += 1) {
    // myMappings[i].title ...
    // myMappings[i].width ...
}

Answer 5

An easier, native and more efficient way of emulating a dict in JavaScript than a hash table:

It also exploits that JavaScript is weakly typed. Rather type inference.

Here's how (an excerpt from Google Chrome's console):

var myDict = {};

myDict.one = 1;
1

myDict.two = 2;
2

if (myDict.hasOwnProperty('three'))
{
  console.log(myDict.two);
}
else
{
  console.log('Key does not exist!');
}
Key does not exist! VM361:8

if (myDict.hasOwnProperty('two'))
{
  console.log(myDict.two);
}
else
{
  console.log('Key does not exist!');
}
2 VM362:4

Object.keys(myDict);
["one", "two"]

delete(myDict.two);
true

myDict.hasOwnProperty('two');
false

myDict.two
undefined

myDict.one
1

Answer 6

Try:

var myMappings = {
    "Name":     "10%",
    "Phone":    "10%",
    "Address":  "50%",
    "Zip":      "10%",
    "Comments": "20%"
}

// Access is like this
myMappings["Name"] // Returns "10%"
myMappings.Name // The same thing as above

// To loop through...
for(var title in myMappings) {
    // Do whatever with myMappings[title]
}