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1. Top results related to what is the difference between the && and & operator in javascript?

   • What is the difference between "in operator" and "includes()" for JavaScript arrays

     Top Answer

     Answered Jan 29, 2018 · 27 votes

     Array.includes()

     checks for the existence of a value in an array, while the in

     operator checks for the existence of a key in an object (or index in the case of arrays).

     Example:

     var arr = [5];console.log('Is 5 is an item in the array: ', arr.includes(5)); // trueconsole.log('do we have the key 5: ', 5 in arr); // falseconsole.log('we have the key 0: ', 0 in arr); // true

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     1/5

   • What is the difference between == and === in JavaScript?

     Top Answer

     Answered Nov 15, 2011 · 20 votes

     • == attempts to convert the values to the same type before testing if they're the same. "5" == 5
     • === does not do this; it requires objects to be of the same type to be equal. "5" !== 5

     In this case, the result is:

     • x == undefined will be true if x is undefined or null.
     • x === undefined will only be true if x is undefined.

     You should prefer the first method if you'd like undefined and null to be treated equivalently. One common use of this is optional function arguments.

     function greet(name, greeting) { if (name == undefined) name = 'World'; if (greeting == undefined) greeting = 'Hello'; alert(greeting + ' ' + name);}greet(); // alerts "Hello World"greet("Bob"); // alerts "Hello Bob"greet(null, "Goodbye"); // alerts "Goodbye World"

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     2/5

   • What is the difference between ' and " in JavaScript?

     Top Answer

     Answered Jun 03, 2009 · 110 votes

     They are equivalent for all intents and purposes. If you want to use either one inside a string, it is a good idea to use the other one to create the string, as you noted. Other than that, it's all the same.

     Other Answers

     Answered Oct 29, 2013 · 55 votes

     Although not technically a difference in Javascript, its worth noting that single quoted strings are not valid JSON, per se. I think that people automatically assume that since JSON is valid JS, that valid JS strings are also valid JSON, which isn't necessarily true.

     E.g., {'key': 'Some "value"'} is not valid JSON, whereas {"key": "Some 'value'"} is.

     Other Answers

     Answered Jun 03, 2009 · 22 votes

     There's no difference. The reason for its existence is exactly what you mentioned

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     3/5

   • What is the difference between Array() and [] in Javascript and why would I use one over the other?

     Top Answer

     Answered Feb 04, 2010 · 4 votes

     new Array(2) proudces an array of size 2, containing two undefineds. [2] produces an array of size 1, containing number 2. new Array IMO doesn't fit with the spirit of JavaScript, even though it may make array construction much more findable. That may or may not be of any importance (I use literals almost exclusively in JavaScript for all applicable types, and I've authored/maintained large pieces of JavaScript [30-50 KLOC] successfully).

     edit I guess the reasons seasoned javascript programmers avoid new Array syntax are:

     • it doesn't behave uniformly across argument numbers and types ( (new Array(X)).length == 1 for any X as long as typeof(X) != "number"
     • it's more verbose and the only thing you gain is the irregularity

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     4/5

   • What is the difference between an array and collection in JavaScript and when should I choose one over the other?

     Top Answer

     Answered Sep 15, 2016 · 2 votes

     From https://developer.mozilla.org/it/docs/Web/API/NodeList:

     Why is NodeList not an Array?

     NodeList are used very much like arrays and it's tempting to invoke Array.prototype methods on them, however NodeList objects don't have any of the familiar Array methods.

     JavaScript has an inheritance mechanism based on prototypes for both built–in objects (like Arrays) and host objects (like NodeLists). Array instances inherit array methods (such as forEach or map) because their prototype chain looks like the following:

     myArray --> Array.prototype --> Object.prototype --> null (The prototype chain of an object can be obtained by calling Object.getPrototypeOf several times.)

     forEach, map and the likes are own properties of the Array.prototype object.

     Unlike arrays, NodeList prototype chain looks like the following:

     myNodeList --> NodeList.prototype --> Object.prototype --> null

     NodeList.prototype contains the item method, but none of the Array.prototype methods, so they cannot be used on NodeLists.

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     5/5

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2. stackoverflow.com › questions › 7310109What's the difference between & and && in JavaScript?

   stackoverflow.com › questions › 7310109

   • Cached

   This operator is almost never used in JavaScript. Other programming languages (like C and Java) use it for performance reasons or to work with binary data. In JavaScript, it has questionable performance, and we rarely work with binary data. This operator expects two numbers and returns a number. In case they are not numbers, they are cast to ...

   Code sample

   if (user.isLoggedIn()) alert("Hello!")

   user.isLoggedIn() && alert("Hello!")

   See more on stackoverflow

3. www.w3schools.com › js › js_comparisonsJavaScript Comparison and Logical Operators - W3Schools

   www.w3schools.com › js › js_comparisons

   • Cached

   When comparing a string with a number, JavaScript will convert the string to a number when doing the comparison. An empty string converts to 0. A non-numeric string converts to NaN which is always false. When comparing two strings, "2" will be greater than "12", because (alphabetically) 1 is less than 2.

4. www.freecodecamp.org › news › difference-betweenDifference between logical operators AND and OR

   www.freecodecamp.org › news › difference-between

   • Cached

   Jun 27, 2023 · The logical AND operator is used between two operands in an expression like this: The operator returns the second operand if the first operand is a truthy value. If the first operand is a falsy value, the operator would return the first operand instead. As we have seen, a truthy value is a value that evaluates to true.

5. stackoverflow.com › questions › 359494Which equals operator (== vs ===) should be used in ...

   stackoverflow.com › questions › 359494

   • Cached

   Dec 11, 2008 · Reference: JavaScript Tutorial: Comparison Operators. The == operator will compare for equality after doing any necessary type conversions. The === operator will not do the conversion, so if two values are not the same type === will simply return false. Both are equally quick.

   • The strict equality operator ( === ) behaves identically to the abstract equality operator ( == ) except no type conversion is done, and the types...
   • Using the == operator ( Equality ) true == 1; //true, because 'true' is converted to 1 and then compared "2" == 2; //true, because "2" is conver...
   • Here's an interesting visualisation of the equality comparison between == and === . Source: https://github.com/dorey/JavaScript-Equality-Table...
   • In the answers here, I didn't read anything about what equal means. Some will say that === means equal and of the same type , but that's not r...
   • Let me add this counsel: If in doubt, read the specification ! ECMA-262 is the specification for a scripting language of which JavaScript is a dia...
   • I tested this in Firefox with Firebug using code like this: console.time("testEquality"); var n = 0; while (true) { n++; if (n == 100000)...
   • In PHP and JavaScript, it is a strict equality operator. Which means, it will compare both type and values.
   • In JavaScript it means of the same value and type. For example, 4 == "4" // will return true but 4 === "4" // will return false
   • Why == is so unpredictable? What do you get when you compare an empty string "" with the number zero 0 ? true Yep, that's right according to...

6. developer.mozilla.org › en-US › docsEquality comparisons and sameness - JavaScript | MDN

   developer.mozilla.org › en-US › docs

   • Cached

   Oct 7, 2023 · If they are of the same type, compare them using step 1. If one of the operands is a Symbol but the other is not, return false. If one of the operands is a Boolean but the other is not, convert the boolean to a number: true is converted to 1, and false is converted to 0. Then compare the two operands loosely again.

7. www.w3schools.com › jsref › jsref_operatorsJavaScript Operators Reference - W3Schools

   www.w3schools.com › jsref › jsref_operators

   • Cached

   JavaScript Operators. Operators are used to assign values, compare values, perform arithmetic operations, and more. There are different types of JavaScript operators: Arithmetic Operators. Assignment Operators. Comparison Operators. Logical Operators. Conditional Operators. Type Operators.

8. People also ask

   What does operator == mean in JavaScript?

   • Operator == Returns true, when both operands are equal. The operands are converted to the same type before being compared. Equality and type comparison: Operator === Returns true if both operands are equal and of the same type. It's generally better and safer if you compare this way, because there's no behind-the-scenes type conversions.

   Which equals operator (== vs ===) should be used in JavaScript

   stackoverflow.com/questions/359494/which-equals-operator-vs-should-be-used-in-javascript-comparisons

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   What is a comparison operator in JavaScript?

   • Reference: JavaScript Tutorial: Comparison Operators The == operator will compare for equality after doing any necessary type conversions. The === operator will not do the conversion, so if two values are not the same type === will simply return false. Both are equally quick.

   Which equals operator (== vs ===) should be used in JavaScript

   stackoverflow.com/questions/359494/which-equals-operator-vs-should-be-used-in-javascript-comparisons

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   Why is a number operator not used in JavaScript?

   • This operator is almost never used in JavaScript. Other programming languages (like C and Java) use it for performance reasons or to work with binary data. In JavaScript, it has questionable performance, and we rarely work with binary data. This operator expects two numbers and returns a number.

   What's the difference between & and && in JavaScript?

   stackoverflow.com/questions/7310109/whats-the-difference-between-and-in-javascript

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   What is the difference between JavaScript === vs ==?

   • JavaScript === vs == . It means equality without type coercion type coercion means JavaScript do not automatically convert any other data types to string data types javaScript convert 2 to string by using == operator integer to string In a typical script there will be no performance difference.

   Which equals operator (== vs ===) should be used in JavaScript

   stackoverflow.com/questions/359494/which-equals-operator-vs-should-be-used-in-javascript-comparisons

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9. javascript.info › logical-operatorsLogical operators - The Modern JavaScript Tutorial

   javascript.info › logical-operators

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   Jun 5, 2022 · The “OR” operator is represented with two vertical line symbols: result = a || b; In classical programming, the logical OR is meant to manipulate boolean values only. If any of its arguments are true, it returns true, otherwise it returns false. In JavaScript, the operator is a little bit trickier and more powerful.