CODEWITHSUNDEEP
javascriptarrays
Aaron
Aaron

Reputation: 3649

JavaScript Array with multiple items

I am trying to create a array with multiple fields in it.

For Example:

var person1 = {firstname:"Bob", lastname:"Smith", middlename:"happy"};

The problem I have is that I have 5000 variables I want to create so it would become:

var person1 = {firstname:"Bob", lastname:"Smith", middlename:"happy"};
var person2 = {firstname:"John", lastname:"Jones", middlename:"Long"};
..
var person5000 = {firstname:"Jim", lastname:"Cook", middlename:"Shorty"};

I think it would be silly to have 5000 lines of code to declare the variables. So I want to be able to declare the variables on page load and then later assign the values to each.

I was trying to do this using the following code but I am guessing I am doing something wrong. (I am loading some dummy data into the variables for testing)

<!DOCTYPE html>
<html>
<body>

<script>
    var person = new Array (firstName:"", lastName:"", middleName:"");
    for (var i = 0; i < 5000; ++i) {
        person[i] = {firstName:"First"+i, lastName:"Last"+i, middlename:"Middle"+i};
    }


alert(person1["firstName"]); // should alert First1
alert(person6["lastname"]);  // should alert Last6


</script>

</body>
</html>

I was hoping to later in my code set the value using: (I am pretty sure this code should work, but can't test it since I can't declare the variables correctly)

person1[firstname] = "Terry";  // should replace First1 with Terry

And then to receive a value using:

alert(person1[firstname]);  // should alert Terry since it was changed

Anyone know what is wrong with my code since it's not returning the value ? I am guessing I am declaring the variables wrong? If so how should I declare them ?

Upvotes: 0

Views: 357

Answers (2)

Barmar
Barmar

Reputation: 781004

You appear to be confused about the difference between arrays and objects in Javascript. Arrays have numeric indexes, objects have named properties. So the initialization 

new Array(firstName:"", lastName:"", middleName:"");

makes no sense. Not to mention, it's not valid Javascript syntax; property: value pairs can only be used in object literals, not in argument lists. If you use new Array(...), the argument should either be a single number, which is the size of the array to allocate, or a list of initial array element (with no property: prefixes. But the preferred way to create a new array is simply with the [] literal for an empty array; it will grow as necessary when you assign to it.

When you create an array, you don't get separate variables for each element. You access them using array[n] notation.

// Create an empty array
var person = [];
// Fill up the array
for (var i = 0; i < 5000; ++i) {
    person[i] = {firstName:"First"+i, lastName:"Last"+i, middlename:"Middle"+i};
}

// Access elements
alert(person[1].firstName);
alert(person[6].middleName);
// Change elements
person[1].firstName = "Terry";

Upvotes: 2

tsnorri
tsnorri

Reputation: 2097

I believe this should work as you intended:

var person = new Array();
for (var i = 0; i < 5000; ++i) {
    person[i] = {firstName:"First"+i, lastName:"Last"+i, middleName:"Middle"+i};
}

alert(person[1]["firstName"]);
alert(person[6]["lastName"]);

As pointed out by others, the person array is filled with objects, not arrays. You can use either property or associative array syntax with them.

Upvotes: 1

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