Created
July 4, 2018 15:17
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/********************************** | |
A symbol is a JavaScript Primitive data type | |
(Number, String, Boolean, null, undefined) | |
Every symbol value returned from Symbol() is unique. | |
A symbol value may be used as an identifier for object properties; this is the data type's only purpose. | |
**********************************/ | |
let log = console.log; | |
const s1 = Symbol(); | |
const s2 = Symbol(123); | |
const s3 = Symbol('steve'); | |
//log(s1); | |
//log(s2); | |
//log(s3); | |
//log(typeof s2); | |
//log(s3.toString() ); | |
//log( Symbol(42) == Symbol(42) ); | |
//log( Symbol(42) === Symbol(42) ); | |
// | |
//log( Symbol.for(123) === Symbol(123) ); | |
//log( Symbol.for(123) === Symbol.for(123) ); | |
//log( Symbol.keyFor(s2) ); | |
//let s5 = Symbol.for(555); | |
//log( Symbol.keyFor(s5) ); | |
// | |
//let obj = {}; | |
//obj['prop1'] = 'value1'; | |
//obj['prop2'] = 'value2'; | |
//obj[Symbol()] = 'value3'; | |
//obj[Symbol()] = 'value3'; | |
//obj[Symbol()] = 'value3'; | |
//obj[Symbol()] = 'value3'; | |
//obj['prop4'] = Symbol() ; | |
// | |
//for( let p in obj){ | |
// log(p, obj[p]); | |
//} | |
//log( JSON.stringify(obj) ); | |
let s4 = Symbol.for('fred'); | |
log(s4); //the symbol created with the key 'fred' | |
// | |
let k4 = Symbol.keyFor(s4); | |
log(k4); | |
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