how to add to a dictionary javascript code example

Example 1: javascript add to a dictionary

for (var i = 0; i < input.length; i++) {
    var datum = input[i];
    if (!d[datum.key]) {
        d[datum.key] = [];
    }
    d[datum.key].push(datum.val);
}

Example 2: javascript add to a dictionary

var d = {}

for (var i in input) {
    var datum = input[i];
    d[datum.key] = datum.val
}