how to compare two strings in javascript if condition

Question

I'm having trouble recalling how to compare these two strings in an if statement. What I'm string to do is check if my variable compare equals page1 or page2 if not, go to the else statement.

var compare = "page3";

if (compare === "page1" || "page2") {
  document.body.innerHTML = "github url";
} else {
  document.body.innerHTML = "non-github url";
}

compare === "page2" ? Seems like an odd question for you to have. — Carcigenicate
– Carcigenicate, Commented Feb 18, 2017 at 18:47

Nina Scholz · Accepted Answer · 2017-02-18 18:47:11Z

19

You could check every option.

if (compare === "page1" || compare === "page2") {

Or you could use an array and check with an existential quantifier like Array#some against, like

if (["page1", "page2"].some(a => a === compare)) {

var compare = "page3";

if (compare === "page1" || compare === "page2") {
    document.body.innerHTML = "github url";
} else {
    document.body.innerHTML = "non-github url";
}

answered Feb 18, 2017 at 18:47

Nina Scholz

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Comments

Kamil Kiełczewski · Accepted Answer · 2020-03-06 18:34:26Z

3

Try

if( ["page1", "page2"].includes(compare) ){...}

var compare = "page3";

if( ["page1", "page2"].includes(compare) ) {
  document.body.innerHTML = "github url";
} else {
  document.body.innerHTML = "non-github url";
}

answered Mar 6, 2020 at 18:34

Kamil Kiełczewski

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2 Comments

jbarradas Over a year ago

Be careful with this approach. In my case, compare can also be page1_other. Which, with this approach, would get wrongly validated.

Kamil Kiełczewski Over a year ago

@jbarradas I check your case compare="page1_other" and includes give false for this case - which is correct (according to OP question)

Scott Marcus · Accepted Answer · 2017-02-18 18:50:39Z

Anytime you have multiple things to check in an if condition, you must write each condition separate from the other. So, the test must be written as:

// If compare equals "page1" OR compare equals "page2"
if (compare === "page1" || compare === "page2") {

When you have a single variable that may contain many different values, using a switch statement can be more logical and more efficient since it only has to look up the value of the variable one time.

Also, remember that strings are literals and "page1" does not equal "Page1". To make a comparison that is case-insensitive, you can force all the values to lower (or upper) case first and then check them against each other (as shown here):

switch (compare.toLowerCase()) {
    case "page1" :
        // Do work here
        break;
    case "page2" :
        // Do work here
        break;
    case "page3" :
        // Do work here
        break;
    default :
        // Do work here
        break;
}

Nagibaba · Accepted Answer · 2020-02-25 20:02:23Z

1

a.localeCompare(b) is another cool way of comparing larger strings

function areEqual(a, b){


  if (a.length !== b.length) {
         return false;
  }

  return a.localeCompare(b) === 0;
}


if(areEqual(a,b)){...}

answered Feb 25, 2020 at 20:02

Nagibaba

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