symbols.js - mozsearch

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/* Any copyright is dedicated to the Public Domain.

 * http://creativecommons.org/licenses/publicdomain/ */

var m = new Map;

// Symbols can be Map keys.

var sym = Symbol();

m.set(sym, "zero");

assertEq(m.has(sym), true);

assertEq(m.get(sym), "zero");

assertEq(m.has(Symbol()), false);

assertEq(m.get(Symbol()), undefined);

assertEq([...m][0][0], sym);

m.set(sym, "replaced");

assertEq(m.get(sym), "replaced");

m.delete(sym);

assertEq(m.has(sym), false);

assertEq(m.size, 0);

// Symbols returned by Symbol.for() can be Map keys.

for (var word of "that that is is that that is not is not is that not it".split(' ')) {

    sym = Symbol.for(word);

    m.set(sym, (m.get(sym) || 0) + 1);

assertDeepEq([...m], [

    [Symbol.for("that"), 5],

    [Symbol.for("is"), 5],

    [Symbol.for("not"), 3],

    [Symbol.for("it"), 1]

]);

if (typeof reportCompare === "function")

  reportCompare(0, 0);