JavaScript Arrays, Hash Tables, and Objects

I’ve been writing a lot of JavaScript lately for SharePoint and when I need to store or manipulate lists of data I cannot remember the JavaScript rules and best practices for using arrays, hash tables, and objects. This post is to remind me of the techniques I’ve learned through research and trial and error.

Hint: You can cut and paste this code into JavaScript try it editor, like http://editor.javascriptkit.com/, and experiment.

JavaScript code

<script type='text/javascript'>

// Instantiate an array

var myArray = [];

// Instantiate a hash table

var myHash = [];

// Instantiate an object hash

var myObjects = []

// If you re-use any of these and need to clear, use the following

myArray.length = 0;

myHash.length = 0;

Object.keys(myObjects).length = 0;

// Add array elements

myArray.push('Dodge');

myArray.push('Audi');

myArray.push('Ford');

// Add hash entries

myHash['Dodge'] = 'RAM 1500';

myHash['Audi'] = 'S4';

myHash['Ford'] = 'Escape';

// Add has object entries

myObjects['Dodge'] = { model: 'RAM 1500', color: 'Blue' };

myObjects['Audi'] = { model: 'S4', color: 'Silver' };

myObjects['Ford'] = { model: 'Escape', color: 'Red' };

// Remove entries

myArray.splice(myArray.indexOf('Audi'), 1);

delete myHash['Audi'];

delete myObjects['Audi'];

// Determine if contains key

document.write('<b>Contains key...</b><br>')

if (myArray.indexOf('Dodge') >= 0) {

    document.write('- found "Dodge" in myArray!<br>');

}

if (myHash['Dodge'] != undefined) {

    document.write('- found "Dodge" in myHash!<br>');

}

if (Object.keys(myObjects).indexOf('Dodge') >= 0) {

    document.write('- found "Dodge" in myObjects!<br>');

}

// Iterate an array

document.write('<br><b>myArray iteration...</b><br>')

for (var i = 0; i < myArray.length; i++) {

    document.write('- myArray: ' + myArray[i] + '<br>')

}

// Iterate a hash

document.write('<br><b>myHash iteration...</b><br>')

for (var key in myHash) {

    document.write('- key/value: ');

    document.write(key + '/');

    document.write(myHash[key] + '<br>');

}

// Iterate a hash of objects

document.write('<br><b>myObjects iteration...</b><br>')

for (var key in myObjects) {

    document.write('- key/model/color: ');

    document.write(key + '/');

    document.write(myObjects[key].model + '/');

    document.write(myObjects[key].color + '<br>');

}

</script>

Output