Merge pull request #373 from int3l/main

Code examples for episode 552

sample_code/ep552/README.md

@@ -0,0 +1,46 @@
+# [what is `Symbol` in js (intermediate)](https://youtu.be/gZBQ8LIR6D4)
+
+I recently was writing some JS and wondered what `Symbol` was -- and now that I know I'm sharing it with you
+
+## Interactive examples
+
+### JavaScript
+
+```javascript
+JSON.stringify({foo: 'hello'})
+o = {toJSON: () => {return {hello: 'hello world'}}}
+JSON.stringify(o)
+
+Symbol
+
+o = {[Symbol.iterator]: function* () { yield 1; yield 2; yield 3; }}
+
+for (let i of o) {
+    console.log(i);
+}
+
+o.iterator
+o[Symbol.iterator]
+
+let fooSymbol = Symbol('foo')
+fooSymbol
+
+Symbol('foo') == fooSymbol
+Symbol('foo') === fooSymbol
+
+let globalFoo = Symbol.for('foo')
+globalFoo == fooSymbol
+
+globalFoo == Symbol.for('foo')
+globalFoo === Symbol.for('foo')
+
+Symbol.keyFor(fooSymbol)
+Symbol.keyFor(Symbol.iterator)
+Symbol.keyFor(globalFoo)
+```
+
+### Bash
+
+```bash
+node
+```