check if object contains string javascript code example

Example 1: How to tell if an attribute exists on an object

const user = {
    name: "Sicrano",
    age: 14
}

user.hasOwnProperty('name');       // Retorna true
user.hasOwnProperty('age');        // Retorna true
user.hasOwnProperty('gender');     // Retorna false
user.hasOwnProperty('address');    // Retorna false

Example 2: js check if string contains character

"FooBar".includes("oo"); // true

"FooBar".includes("foo"); // false

"FooBar".includes("oo", 2); // false

Example 3: check if object has method javascript

if(typeof myObj.prop2 === 'function') {
    alert("It's a function");
} else if (typeof myObj.prop2 === 'undefined') {
    alert("It's undefined");
} else {
    alert("It's neither undefined nor a function. It's a " + typeof myObj.prop2);
}

Example 4: js does object contain value

// You can turn the values of an Object into an array.
// Then test that a value is present:

// This assumes, that the Object is not nested
// and the value is an exact match:

var obj = { a: 'test1', b: 'test2' };

// Note that an array can only have positive index's; so
// checking for a negative index is a super valid way for getting a
// boolean value as a result for the check.
if (Object.values(obj).indexOf('test1') > -1) {
   console.log('Value exists!');
}

Example 5: includes in javascript

var colors = ['yellow', 'red', 'pink'];
var string = 'yellow and red are pretty cool';

// outputs false
console.log(colors.include('blue');
// outputs true
console.log(string.includes('yellow');