ES6 version of this is (check out answer from Allison):

!str1.includes(str2)

The original accepted answer was:

You are looking for indexOf

var x = "home.subjects.subject.exams.exam.tests";
console.log(x.indexOf('subjects'));     // Prints 5
console.log(x.indexOf('state'));        // Prints -1

The value returned by .getElementsByTagName() is not an array, it is a live HTMLCollection . You need to convert it to an array if you want to use array methods on it. Also keep in mind that Array.prototype.includes has poor browser support, so you need to polyfill it. But even then your code won't work. Your code is saying "does this array of elements contain the string "*"" - to which the answer is obviously always no, because there is no case where a element === the string "*". Assuming that the user input is rendered to straight HTML (i.e. the user input isn't inside a or <input>) then you need to check if the .textContent of any of your cells contains the string "*" - how you want to do that depends on how you are in regards to browser support/transpiling to ES5. Assuming cells is your array (not your HTMLCollection), then the ES6 way would be if (cells.some(td => td.textContent.includes("*")) { ... } - while the ES5 way would be a plain ol' for loop to check through each value in the array, checking if .textContent.indexOf("*") !== -1.

Just negate it.

filteredResult = filteredResult.filter(e => !e.selectedFields.includes("Red"))

As we could see in the image pasted in comments (why you should not doing that), you don't have an arrays of emails, you have an array of objects that includes an email in some of their properties (email).

You could use Array.prototype.some() to return true or false if some element is present passing a function as parameter items.some(o => o.email === mail) Array.prototype.includes() doesn't accept a functions as parameter.

var items = [{
    "email": "[email protected]"
  },
  {
    "email": "[email protected]"
  },
  {
    "email": "[email protected]"
  }
]


var mail = "[email protected]";

var mail2 = "[email protected]";

(items.some(o => o.email === mail)) ? console.log(true): console.log(false);

(items.some(o => o.email === mail2)) ? console.log(true): console.log(false);

Finally, please read why we shouldn't paste images of code: https://meta.stackoverflow.com/a/285557/6121568

Because Array in js is a specific object, the [2,4] inside myArray is object and [2,4] that you switch to includes is anther object. If you want that includes return true you must do this:

var array = [2, 4]

const myArray = [array, "cat", "hamster", 9]

console.log(myArray.includes(array))

If you look at the documentation of includes(), most of the browsers don't support this property.

You can use widely supported indexOf() after converting the property to string using toString():

if ($(".right-tree").css("background-image").indexOf("stage1") > -1) {
//                                           ^^^^^^^^^^^^^^^^^^^^^^

You can also use the polyfill from MDN.

if (!String.prototype.includes) {
    String.prototype.includes = function() {
        'use strict';
        return String.prototype.indexOf.apply(this, arguments) !== -1;
    };
}

There is an operator to negate boolean values.

The Javascript you can run within node / v8 has a function, includes(), on all arrays, which returns a boolean, indicating whether the element is present in the array or not. Apigee doesn’t use node/v8 for its Javascript engine. Apigee uses Rhino. (I think the version of Rhino used within Apigee is…