Not able to compare strings in Javascript

Question

I am trying to compare a string with a set of strings stored in an array. Here is the block of code:

then(op => {
        if (op[0].probability > FILTER_THRESHOLD) {
          if (FILTER_LIST.indexOf(op[0].className) > 1) {
            console.log("EUREKA! EUREKA! EUREKA!")

            console.log(op[0].className)
            return true;
          }
        }
        return false;
      })

The second if statement should evaluate to true in some cases but it is not. The return is always false.

op[0].className should be a string and I am also able to get the value from op[0].probability correctly.

What could be the reason?

I have tried debugging and cannot seem to get why the 'if' statement is not being true.

Here is the FILTER_LIST array:

var FILTER_LIST = ["Hello", "Please", "Simple"];

Please advise how I can fix this!

Thank you!

So they should match perfectly right? Or am I missing something? — Navendu Pottekkat
– Navendu Pottekkat, Commented Jul 9, 2020 at 18:15
Take a look at the answer below as to why your if logic is flawed. — Taplar
– Taplar, Commented Jul 9, 2020 at 18:16

T.J. Crowder · Accepted Answer · 2020-07-09 18:14:20Z

2

indexOf(...) > 1 asks "did it find a match at the third element or later?" You'll get false if it matched at index 0 or 1. If you want just "it found one anywhere", you want !== -1, >= 0, or to use includes instead of indexOf.

if (FILTER_LIST.indexOf(op[0].className) !== -1) {
// or
if (FILTER_LIST.indexOf(op[0].className) >= 0) {
// or
if (FILTER_LIST.includes(op[0].className)) {

answered Jul 9, 2020 at 18:14

community wiki

T.J. Crowder

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5 Comments

Navendu Pottekkat Over a year ago

Let me check that

Navendu Pottekkat Over a year ago

It did not work as expected. The logic is correct but for some reason it is still returning false. What could be the reason??

T.J. Crowder Over a year ago

@NavenduPottekkat - Your best bet here is to put a breakpoint on the line and look closely at the array and at the string you're checking. Alternatively, please update your question with a minimal reproducible example demonstrating the problem, ideally a runnable one using Stack Snippets (the [<>] toolbar button; here's how to do one). My guess is className has another class in it, or a space at the beginning, or at the end, etc., etc.

Navendu Pottekkat Over a year ago

The problem is I have to build this code. i.e I use parcel to build this js file and that file is run in the browser. In that case, how would I be able to debug?

T.J. Crowder Over a year ago

@NavenduPottekkat - Use the debugger built into the browser.

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