Initializing an Array with a Single Value

This is an old question, but I use this in modern JS:

[...new Array(1000000)].map(()=>42);

while(arraySize--) array.push(value);

no initialization (that i know of)

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Update

Since ever posting this answer 4 years ago, people seem to keep coming back here for this answer. For benchmarking purposes I made a JSPerf with some different solutions.

The solution above here isn't the quickest, although it's short. To stick to the same short style, but with a better performance:

while(size--) array[size] = value;

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Update Feb 2016 Updated the JSPerf with a new revision with more testcases.

If performance doesn't matter and you want a one-liner:

var value = 1234, // can be replaced by a fixed value
    size  = 1000, // can be replaced by a fixed value
    array = Array.apply(null,{length: size}).map(function() { return value; });

A more performant solution (in one, dirty, line): Be aware: this replaces existsing value, size and i variables in the scope

for(var i = 0, value = 1234, size = 1000, array = new Array(1000); i < size; i++) array[i] = value;

One short way of doing it would be:

var arr = Array(arraySize).fill(value);

Would make arr = Array [ 0, 0, 0, 0, 0 ] if arraySize == 5 and value == 0, for example.