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.

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.

• javascript
• arrays
• match

• 2 Use indexOf – Prateek Commented Dec 3, 2014 at 4:24
• 1 names.indexOf(returnedValue) – Leo Commented Dec 3, 2014 at 4:24
• possible duplicate of JavaScript find array index with value – user663031 Commented Dec 3, 2014 at 4:32
• filter() would be used to count or find all the matches instead of just the first (or last via lastIndexOf()) – dandavis Commented Dec 3, 2014 at 4:32
• names.contains works in es6 – Shiala Commented Jan 28, 2015 at 17:56

3 Answers 3

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./a/12623295/2934820

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

Check out this link on dictionaries https://www.w3schools./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)