If variable is equal to value or another value - javascript

Question

I'm trying to write a simple Pig Latin code. I want to check if the first letter of the input string is a vowel, if so then to run that certain code. How can I ask if y is equal to one of those values.

function pigLatin() {
    var y = prompt("Enter a word:")
    if (y.charAt(0) = a,e,i,o,u) {
        var pigLatin = y + "ay";
        document.getElementById("answer").innerHTML = "Answer is: " + pigLatin;
    } else {
        var wordLength = y.length + 1;
        var pigLatin = y.substring(1, wordLength) + y.charAt(0) + "ay";
        document.getElementById("answer").innerHTML = "Answer is: " + pigLatin;
    }
}

= assigns, == or === checks for equality (apart from the invalid syntax a,e,i,o,u) — baao, Sep 12 '17 at 08:53
Please see [**Equality comparisons**](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Equality_comparisons_and_sameness) — Nope, Sep 12 '17 at 08:55
Possible duplicate of several SO posts in relation to equality of which one is https://stackoverflow.com/questions/359494/which-equals-operator-vs-should-be-used-in-javascript-comparisons — Nope, Sep 12 '17 at 08:56

alex · Accepted Answer · 2017-09-12T09:02:24.153

8

if (y.charAt(0) = a,e,i,o,u) {

...is not valid.

Try...

if ('aeiou'.includes(y.charAt(0))) {

Your problems are...

Strings must be quoted, even if they're only one character long.
An array must be wrapped with [ and ] (unless constructed via another means such as with the Array constructor)
You can't use the assignment operator (=), nor any equivalency operator (== or ===) to automatically check for the presence of an item in an array. Since you're checking against a list of single characters, you can directly use String.prototype.includes() on it.

If the user cancels the prompt(), you will get null also, which you are not handling (it will crash on the condition mentioned).

edited Sep 12 '17 at 09:02

answered Sep 12 '17 at 08:53

alex

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Or perhaps `if ('aeiou'.includes(y.charAt(0))) {`. – user94559 Sep 12 '17 at 08:54
@Rajesh That regular expression is wrong. Maybe you meant `/[aeiou]/`? (I'd argue this is a bad use case for a regular expression anyway.) – user94559 Sep 12 '17 at 08:56
@Rajesh While it could work, I don't see the need to use a regex over normal string methods – alex Sep 12 '17 at 08:56
This is the first time asking a question on here. You guys are amazing people <3 – user3359079 Sep 12 '17 at 09:58

doctorlove · Answer 2 · 2017-09-12T09:07:21.690

0

First, you need the letters to be in quotes in this

if (y.charAt(0) = a,e,i,o,u)

Second, use === for equals.

Third you want it to be one of the vowels 'a', 'e', 'i', 'o', 'u'.

You could compare the indexOf the char against -1:

if (['a', 'e', 'i', 'o', 'u'].indexOf(y.charAt(0)) !== -1)
//...

edited Sep 12 '17 at 09:07

answered Sep 12 '17 at 08:55

doctorlove

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`in` doesn't work like that. It checks for keys in an object, here you have an array of chars. – alex Sep 12 '17 at 08:57
Of course; that gets an index.. the other answer is better anyway. – doctorlove Sep 12 '17 at 09:07

If variable is equal to value or another value - javascript

2 Answers2