String.indexof() always saying iam -1?

Question

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I have a javascript function to find the index of an array like this

JavaScript

function myFunction() {
  var fruits = ["Lesson%202%20*,Lesson%203,Lesson%201%20*,"];
  var a = fruits.indexOf("Lesson%203");
  document.getElementById("demo").innerHTML = a;
}

this array always result in -1 which is wrong!!

while this function below

JavaScript

function myFunction() {
  var fruits = ["Banana", "Orange", "Apple", "Mango"];
  var a = fruits.indexOf("Apple");
  document.getElementById("demo").innerHTML = a;
}

return the index as 2 which is correct.

what I have been missing here can somebody explain the logic behind this?

What I have tried:

the code i have tried is shown above

Posted 8-Jul-19 2:18am

Member 14052128

Updated 8-Jul-19 5:25am

v3

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CHill60 8-Jul-19 8:20am

In your first example you only have a single entry in the array - compare where the quotes are between the two examples

Member 14052128 8-Jul-19 8:25am

ok that was a typo i did while typing question sorry for that can u find any other error?

CHill60 8-Jul-19 8:44am

I presume you still have a typo then - even after your correction you still only have a single string in that array. Do as @Dave-Kreskowiak suggests and paste your code into your question. It should be

var fruits = ["Lesson%202%20*","Lesson%203","Lesson%201%20*,"];

2 solutions

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Anurag Gandhi · Accepted Answer · 2019-07-08T05:26:00

Solution 2

Hi,
There is basic typo while declaring fruits array. After correction:

function myFunction() {
  var fruits = ["Lesson%202%20*", "Lesson%203", "Lesson%201%20*,"];
  var a = fruits.indexOf("Lesson%203");
  document.getElementById("demo").innerHTML = a;
}

This returns 1. Which is as expected.

Posted 8-Jul-19 5:26am

Anurag Gandhi

Comments

Member 14052128 8-Jul-19 23:44pm

thankyou for correcting me :)

CHill60 9-Jul-19 7:12am

Actually it was me that corrected you, 2 hours before this solution was posted!

Dave Kreskowiak · Accepted Answer · 2019-07-08T02:33:00

You've got an array of only a single string and you're looking for a string entry in the array that doesn't match. You are expecting the IndexOf method to find substrings in the array elements and that's not what it does.

"Lesson%203" is not equal to "Lesson%202%20*,Lesson%203,Lesson%201%20*,".

As you said, this may be a typo. If it is, do NOT type the code. Copy and paste the EXACT code you're using.