Using .includes method in a function

You can use String.indexOf() instead of String.includes, As it is available in ES6 and not supported in IE at all.

typeof value == "string" && value.indexOf('$') > -1

Also note if value is not string type it will still raise an error boolean, Number doesn't the the method. You can use typeof to validate whether value is a string.

The .includes() API is part of the String and Array data type.

So what the error is trying to tell you is that the value for variable value, e.g. an integer or object, does not have the property .includes.

You could do checks like

1. typeof a_string === 'string'
2. an_array instanceof Array

before the .includes() api to prevent this.

Obviously this will make your if statement rather ugly due to the number of checks you have.

Based on the way your code is written I suspect you are more interested in checking "String" than array. So becareful of arrays. Your code may not work properly if it is array.

Anyway here is a refractored version of your code.

function replacer(key, value) {
   // Filtering out properties
   if (!value || typeof value === "string" && value.includes("$")) {
        return undefined;
   }
   return value;
 } 

console.log("NULL returns:" + replacer('test', null));
console.log("$Test returns:" + replacer('test', '$test'));
console.log("Blah returns:" + replacer('test', 'Blah'));

I solved this error, which I was getting when applying "includes" to a "window.location" value, by appending ".toString();"

var requestUrl = window.location.toString();

if (requestUrl.includes(urlBase + "#")) { ...

Just one more possibility: Maybe your value is not a string type object.

(typeof(value) == "string" && value.includes("$"))