How to match a variable value against an array of values in Javascript?

Question

I have an array of values with names:

names = ['Jim', 'Jack', 'Fred']

I have also received a value from a function, which is a name in string form, such as:

returnedValue = 'Jim'

How can I run the returnedValue string against the values of the names array and test for a match?

My feeling is that you would want to use the .filter method of the array prototype but I can't conceive of how to do it that way.

Use **[indexOf](http://www.w3schools.com/jsref/jsref_indexof_array.asp)** — Prateek, Dec 03 '14 at 04:24
possible duplicate of [JavaScript find array index with value](http://stackoverflow.com/questions/7346827/javascript-find-array-index-with-value) — , Dec 03 '14 at 04:32
filter() would be used to count or find all the matches instead of just the first (or last via lastIndexOf()) — dandavis, Dec 03 '14 at 04:32

score 11 · Accepted Answer · edited May 23 '17 at 12:28

11

There is an indexOf method that all arrays have (except in old version of Internet Explorer) that will return the index of an element in the array, or -1 if it's not in the array:

if (yourArray.indexOf("someString") > -1) {
    //In the array!
} else {
    //Not in the array
}

If you need to support old IE browsers, you can use polyfill this method using the code in the MDN article.

Copied from https://stackoverflow.com/a/12623295/2934820

edited May 23 '17 at 12:28

Community

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answered Dec 03 '14 at 04:26

Sharon

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I was looking allll over the internet for this. THANK YOU! – Char Aug 01 '18 at 08:14

score 0 · Answer 2 · answered Dec 03 '14 at 04:31

the Array.indexOf method will return a value with the position of the returned value, in this case 0, if the value is not in array you'd get back -1 so typically if you wanna know if the returnedValue is in the array you'd do this if (names.indexOf(returnedValue) > -1) return true; Or you can do ~~ like Mr. Joseph Silber kindly explains in another thread

score -1 · Answer 3 · answered Feb 19 '20 at 20:58

Check out this link on dictionaries https://www.w3schools.com/python/python_dictionaries.asp If you have a variable whose value would match a string in the dictionary you can set a variable to equal that value. Here is a snip from some of my own code`

global element1
element1 = 1
elementdict = {
"H": 1.008,
"He": 4.00,
"Li": 6.49,
"Be": 9.01,
"B": 10.81,
"C": 12.01,
"N": 14.01,
"O": 16.00,
"F": 19.00,
"Ne": 20.18,
"Na": 22.99,
"Mg": 24.30
}
element1 = input("Enter an element to recieve its mass")
element1 = elementdict[element1]
print(element1)

Welcome to SO! You might want to review [How do I write a good answer?](https://stackoverflow.com/help/how-to-answer). The answer you provided is for Python and the question was about JavaScript. — displacedtexan, Feb 19 '20 at 21:04

How to match a variable value against an array of values in Javascript?

3 Answers3