how to create a key value pair dictionary in javascript code example

Example 1: javascript add to a dictionary

obj["key3"] = "value3";

Example 2: 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);
}