Javascript - Loop through sparse array and replace sparse values -


i'm trying loop through sparse array , fill in sparse elements value.

['foo', 'bar', , , ,].map(el => el || 'default') // returns ["foo", "bar", undefined × 3]

how return ["foo", "bar", "default", "default", "default", "default"]

since .map (and .foreach) skip sparse values there's no option except use loop, should explicitly check absence of missing keys

for (var = 0, n = a.length; < n; ++i) {     if (!(i in a)) {       // explicit check missing sparse value         a[i] = "default";     } }

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