How lodash "_.every" works with an empty predication param?

Question

I want to replace lodash _.every method with the native every from Array.prototype.

I faced with the case when array is checked with the empty predication like this _.every(arr).

What should I place into a native every method to get the same result as in the lodash?

Answer 1

From the documentation, the _.every() function takes the _.identity() as the default predicate.

So we can substitute the function v => v for this (the identity function simply returns the first argument).

const testInputs = [[true, false], [true, true], [false, false], [false, true]]

for(let i = 0; i < testInputs.length; i++) {
    console.log(`Test #${i+1}`);
    console.log('_.every():', _.every(testInputs[i]));
    console.log('Array.every():', testInputs[i].every(v => v));
}

.as-console-wrapper { max-height: 100% !important; }

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