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Commit e2f9af3

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Number Methods and Symbol Added
1 parent 3b1462c commit e2f9af3

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13 files changed

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let number = 10;
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console.log(number.toExponential(1));
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// JavaScript Number toExponential()
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// The JavaScript Number toExponential() method returns a string representing the Number object in exponential notation.
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// The syntax of the toExponential() method is:
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// num.toExponential(fractionDigits)
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// Here, num is a number.
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// Number toExponential() Parameters
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// The toExponential() method takes in:
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//
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// fractionDigits (Optional) - An integer specifying the number of digits after the decimal point. By default, it is as many digits as necessary to specify the number.
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// Return value from Number toExponential()
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// Returns a string representing the given Number object in exponential notation, rounded to fractionDigits digits after the decimal point.
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// Example: Using Number.toExponential()
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let num = 695.8457;
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let exp_num = num.toExponential();
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console.log(exp_num); // 6.958457e+2
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let exp_num1 = num.toExponential(2);
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console.log(exp_num1); // 6.96e+2
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// Run Code
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// Output
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6.958457e+2
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6.96e+2

‎12. Symbol in JavaScript/1.js‎

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// JavaScript Symbol
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// The JavaScript ES6 introduced a new primitive data type called Symbol. Symbols are immutable (cannot be changed) and are unique. For example,
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// two symbols with the same description
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const value1 = Symbol('hello');
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const value2 = Symbol('hello');
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console.log(value1 === value2); // false
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// Though value1 and value2 both contain the same description, they are different.

‎12. Symbol in JavaScript/2.js‎

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// Creating Symbol
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// You use the Symbol() function to create a Symbol. For example,
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// creating symbol
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const x = Symbol();
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console.log(typeof x); // symbol
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// You can pass an optional string as its description. For example,
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const x1 = Symbol("hey");
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console.log(x1); // Symbol(hey)

‎12. Symbol in JavaScript/3.js‎

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// Access Symbol Description
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// To access the description of a symbol, we use the . operator. For example,
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const x = Symbol('hey');
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console.log(x.description); // hey

‎12. Symbol in JavaScript/4.js‎

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// Add Symbol as an Object Key
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// You can add symbols as a key in an object using square brackets []. For example,
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let id = Symbol("id");
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let person = {
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name: "Jack",
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// adding symbol as a key
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[id]: 123 // not "id": 123
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};
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console.log(person); // {name: "Jack", Symbol(id): 123}

‎12. Symbol in JavaScript/5.js‎

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// Symbols are not included in for...in Loop
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// The for...in loop does not iterate over Symbolic properties. For example,
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let id = Symbol("id");
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let person = {
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name: "Jack",
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age: 25,
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[id]: 12
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};
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// using for...in
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for (let key in person) {
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console.log(key);
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}

‎12. Symbol in JavaScript/6.js‎

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// Benefit of Using Symbols in Object
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// If the same code snippet is used in various programs, then it is better to use Symbols in the object key. It's because you can use the same key name in different codes and avoid duplication issues. For example,
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let person = {
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name: "Jack"
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};
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// creating Symbol
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let id = Symbol("id");
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// adding symbol as a key
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person[id] = 12;
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// In the above program, if the person object is also used by another program, then you wouldn't want to add a property that can be accessed or changed by another program. Hence by using Symbol, you create a unique property that you can use.
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// Now, if the other program also needs to use a property named id, just add a Symbol named id and there won't be duplication issues. For example,
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person = {
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name: "Jack"
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};
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let id1 = Symbol("id");
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person[id1] = "Another value";
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// In the above program, even if the same name is used to store values, the Symbol data type will have a unique value.
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// In the above program, if the string key was used, then the later program would have changed the value of the property. For example,
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person = {
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name: "Jack"
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};
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// using string as key
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person.id = 12;
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console.log(person.id); // 12
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// Another program overwrites value
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person.id = 'Another value';
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console.log(person.id); // Another value
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// In the above program, the second user.id overwrites the previous value.
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‎12. Symbol in JavaScript/7.js‎

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// Symbol Methods
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// There are various methods available with Symbol.
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// Method Description
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// for() Searches for existing symbols
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// keyFor() Returns a shared symbol key from the global symbol registry.
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// toSource() Returns a string containing the source of the Symbol object
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// toString() Returns a string containing the description of the Symbol
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// valueOf() Returns the primitive value of the Symbol object.
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// Example: Symbol Methods
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// get symbol by name
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let sym = Symbol.for('hello');
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let sym1 = Symbol.for('id');
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// get name by symbol
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console.log( Symbol.keyFor(sym) ); // hello
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console.log( Symbol.keyFor(sym1) ); // id

‎12. Symbol in JavaScript/8.js‎

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// Symbol Properties
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// Properties Description
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// asyncIterator Returns the default AsyncIterator for an object
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// hasInstance Determines if a constructor object recognizes an object as its instance
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// isConcatSpreadable Indicates if an object should be flattened to its array elements
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// iterator Returns the default iterator for an object
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// match Matches against a string
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// matchAll Returns an iterator that yields matches of the regular expression against a string
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// replace Replaces matched substrings of a string
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// search Returns the index within a string that matches the regular expression
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// split Splits a string at the indices that match a regular expression
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// species Creates derived objects
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// toPrimitive Converts an object to a primitive value
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// toStringTag Gives the default description of an object
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// description Returns a string containing the description of the symbol
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// Example: Symbol Properties Example
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const x = Symbol('hey');
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// description property
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console.log(x.description); // hey
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const stringArray = ['a', 'b', 'c'];
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const numberArray = [1, 2, 3];
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// isConcatSpreadable property
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numberArray[Symbol.isConcatSpreadable] = false;
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let result = stringArray.concat(numberArray);
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console.log(result); // ["a", "b", "c", [1, 2, 3]]

‎Pratice/21.js‎

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let a = 1;
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let b = 2;
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let c = "1";
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let name = "Hello";
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let name1 = "Hello";
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let name2 = "hello";
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console.log(a == b); // false
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console.log(a == c); // true
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console.log(name == name1); // true
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console.log(name == name2); // false
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console.log(name === name1);
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