JavaScript Array with multiple items
Question
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 ?
2 answers
solution1
2 ACCPTED 2014-11-10 00:53:19
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";
solution2
1 2014-11-10 00:53:12
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.
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