Convert object array to hash map, indexed by an attribute value of the Object

Question

Use Case

The use case is to convert an array of objects into a hash map based on string or function provided to evaluate and use as the key in the hash map and val

Answer 1

Using ES6 Map (pretty well supported), you can try this:

var arr = [
    { key: 'foo', val: 'bar' },
    { key: 'hello', val: 'world' }
];

var result = new Map(arr.map(i => [i.key, i.val]));

// When using TypeScript, need to specify type:
// var result = arr.map((i): [string, string] => [i.key, i.val])

// Unfortunately maps don't stringify well.  This is the contents in array form.
console.log("Result is: " + JSON.stringify([...result])); 
// Map {"foo" => "bar", "hello" => "world"}