Published
Edited
Jan 23, 2020
3 stars
{
const foo1 = Symbol('foo');
const foo2 = Symbol('foo');
assert(foo1 !== foo2);
assert(foo1.description === foo2.description);
}
Symbol('A handy description')
new Symbol()
Symbol() instanceof Symbol
typeof Symbol()
typeof String()
typeof new String()
{
const foo1 = Symbol.for('foo');
const foo2 = Symbol.for('foo');
assert(foo1 === foo2);
}
{
const iframe = document.createElement('iframe');
document.body.appendChild(iframe);
assert.equal(iframe.contentWindow.Symbol.for('foo'), Symbol.for('foo'));
assert.notEqual(iframe.contentWindow.Symbol, Symbol);
assert.notEqual(iframe.contentWindow.Symbol.for('foo'), Symbol('foo'));
}
{
const foo1 = Symbol('foo');
const foo2 = Symbol.for('foo');
assert(Symbol.keyFor(foo1) === undefined);
assert(Symbol.keyFor(foo2) === 'foo');
}
{
const foo = Symbol();
'' + foo;
}
{
const foo = Symbol();
+foo;
}
{
const obj = {};
const foo = Symbol();
obj[foo] = 'bar';
assert.deepEqual(Object.getOwnPropertyNames(obj), []);
assert.deepEqual(Object.entries(obj), []);
}
{
const obj = {};
const foo = Symbol();
obj[foo] = 'bar';
assert.deepEqual(Object.getOwnPropertySymbols(obj), [foo]);
assert(obj[foo] === 'bar');
}
{
class MyIterableClass {
*[Symbol.iterator]() {
yield 'I';
yield 'like';
yield 'pizza';
}
}
const instance = new MyIterableClass();
const results = [];
for (const result of instance) {
results.push(result);
}
return results;
}
Purpose-built for displays of data
Observable is your go-to platform for exploring data and creating expressive data visualizations. Use reactive JavaScript notebooks for prototyping and a collaborative canvas for visual data exploration and dashboard creation.
