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This is a playground to test code. It runs a full Node.js environment and already has all of npm’s 1,000,000+ packages pre-installed, including @extra-array/count-on. Try it out:
const array = require('extra-array');
var x = [1, 1, 2, 2, 4];
array.countOn(x);
var x = [1, 2, 3, 4];
array.countOn(x, v => v % 2);
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awaitany promise instead of using callbacks (example)- create your own embedded node.js snippets
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