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JavaScriptBeginner#es6
JavaScriptBeginner#arrays
What do find, findIndex, some and every do?
find returns the first matching element, findIndex its index, some returns true if any element matches, every returns true only if all match. some and every short-circuit.
Example
const u = [{age:17},{age:22}];
u.find(x => x.age > 18); // {age:22}
u.some(x => x.age > 18); // true
u.every(x => x.age > 18); // false