How to return array in variable instead of string javascript

Question

var i = 1

var pattern1 = ["apple", "pear", "orange", "carrot"]

var pattern2 = ["apple", "pear", "orange", "carrot"]

var currentPat = "pattern" + i

alert(currentPat)

The currentPat variable is returning the string pattern1, its not returning the array. What am i doing wrong?

try pattern1[i]. Note that broken code isn't a great substitute for a properly detailed explanation of what you are trying to accomplish — charlietfl
– charlietfl, Commented Jan 7, 2018 at 0:34
Why should it return something different? Your variable currentPat is simply a string. A string has nothing to do with the variable name itself. — meow
– meow, Commented Jan 7, 2018 at 0:35
@charlietfl the pattern is always changing so i need to be able to change the number in pattern1 — Matt
– Matt, Commented Jan 7, 2018 at 0:35
var currentPat = window["pattern" + i] does what you want. — connexo
– connexo, Commented Jan 7, 2018 at 0:35
Anytime you find yourself munging together numbers into variable names to access your data, you should probably be using an array. Concatenating text and numbers to address variables will get out of hand very quickly and Javascript gives you an abundance of better alternatives. See @mdatsev's answer below. — Mark
– Mark, Commented Jan 7, 2018 at 0:44

mdatsev · Accepted Answer · 2018-01-07 00:37:33Z

2

You should have the patterns as 2 elements of an array and then you can use this:

var i = 1
var pattern = [];
pattern[1] = ["apple", "pear", "orange", "carrot"] 
pattern[2] = ["apple", "pear", "orange", "carrot"] 
var currentPat = pattern[i]
alert(currentPat)

If you can't change how the patterns are defined you could use eval("pattern"+i) but this isn't recommended since it makes the code harder to read and could lead to some security problems if used with user input.

answered Jan 7, 2018 at 0:37

mdatsev

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connexo · Accepted Answer · 2018-01-07 00:45:49Z

2

To use a variable property name, you need to access that via the square brackets syntax:

var i = 1

var pattern1 = ["apple", "pear", "orange", "carrot"]

var pattern2 = ["apple", "pear", "orange", "carrot"]

var currentPat = window["pattern" + i]

console.log(currentPat)

Because both pattern1 and pattern2 are global variables in your example, they automatically become properties of the global object (which in a browser, is the window object).

window.pattern1

does exactly the same as

var prop = "pattern1"
window[prop]

or as

window["pattern1"]

edited Jan 7, 2018 at 0:45

answered Jan 7, 2018 at 0:40

connexo

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