HashMapString

type key = string;

Type of the Belt.HashMap.String key.

type t('b);

Type of the Belt.HashMap.String.

let make: (~hintSize: int) => t('b);

make(~hintSize=10) creates a new hash map by taking the hintSize.

RE

let hMap = Belt.HashMap.String.make(~hintSize=10);

Belt.HashMap.String.set(hMap, "key1", "a");

let clear: t('b) => unit;

Clears a hash table.

RE
let hMap = Belt.HashMap.String.fromArray([|("1", "1")|])  
Belt.HashMap.String.clear(hMap)
Belt.HashMap.String.isEmpty(hMap) == true;

let isEmpty: t('a) => bool;

isEmpty(m) checks whether a hash map is empty.

RE
let hMap = Belt.HashMap.String.fromArray([|("1", "1")|])  
Belt.HashMap.String.isEmpty(hMap) == false;

let set: (t('a), key, 'a) => unit;

set(tbl, k, v) if k does not exist, add the binding k,v, otherwise, update the old value with the new v.

RE
 
let hMap = Belt.HashMap.String.fromArray([|("2", "2")|]);

Belt.HashMap.String.set(hMap, "1", "1");

Belt.HashMap.String.valuesToArray(hMap) == [|"1", "2"|];

let copy: t('a) => t('a);

Creates copy of a hash map.

RE
let hMap1 = Belt.HashMap.String.fromArray([|("1", "1"), ("2", "2")|]);
let hMap2 = Belt.HashMap.String.copy(hMap1)

Belt.HashMap.String.set(hMap2, "2", "3");

Belt.HashMap.String.get(hMap1, "2") != Belt.HashMap.String.get(hMap2, "2")

let get: (t('a), key) => option('a);

Returns value bound under specific key. If values not exist returns None.

RE
let hMap = Belt.HashMap.String.make(~hintSize=10);
Belt.HashMap.String.set(hMap, "1", "value1");

Belt.HashMap.String.get(hMap, "1") == Some("value1");
Belt.HashMap.String.get(hMap, "2") == None;

let has: (t('b), key) => bool;

Checks if x is bound in tbl.

RE
let hMap = Belt.HashMap.String.make(~hintSize=10);
Belt.HashMap.String.set(hMap, "1", "value1");

Belt.HashMap.String.has(hMap, "1") == true;
Belt.HashMap.String.has(hMap, "2") == false;

let remove: (t('a), key) => unit;

If bound exists, removes it from the hash map.

RE
let hMap = Belt.HashMap.String.make(~hintSize=10);
Belt.HashMap.String.set(hMap, "1", "value1");
Belt.HashMap.String.remove(hMap, "1");
Belt.HashMap.String.has(hMap, "1") == false;

let forEachU: (t('b), [@bs] ((key, 'b) => unit)) => unit;

Same as forEach but takes uncurried functon.

let forEach: (t('b), (key, 'b) => unit) => unit;

forEach(tbl, f) applies f to all bindings in table tbl. f receives the key as first argument, and the associated value as second argument. Each binding is presented exactly once to f.

RE
let hMap = Belt.HashMap.String.make(~hintSize=10);
Belt.HashMap.String.set(hMap, "1", "value1");
Belt.HashMap.String.forEach(hMap, (key, value) => Js.log2(key, value));
// prints ("1", "value1")

let reduceU: (t('b), 'c, [@bs] (('c, key, 'b) => 'c)) => 'c;

Same as reduce but takes uncurried functon.

let reduce: (t('b), 'c, ('c, key, 'b) => 'c) => 'c;

reduce(tbl, init, f) computes (f(kN, dN) ... (f(k1, d1, init))...), where k1 ... kN are the keys of all bindings in tbl, and d1 ... dN are the associated values. Each binding is presented exactly once to f.

The order in which the bindings are passed to f is unspecified. However, if the table contains several bindings for the same key, they are passed to f in reverse order of introduction, that is, the most recent binding is passed first.

RE
let hMap = Belt.HashMap.String.make(~hintSize=10);
Belt.HashMap.String.set(hMap, "1", "value1");
Belt.HashMap.String.set(hMap, "2", "value2");

Belt.HashMap.String.reduce(hMap, "", (acc, key, value) => {
  acc ++ ", " ++ value
}) == "value1, value2";

let keepMapInPlaceU: (t('a), [@bs] ((key, 'a) => option('a))) => unit;

Same as keepMapInPlace but takes uncurried functon.

let keepMapInPlace: (t('a), (key, 'a) => option('a)) => unit;

Filters out values for which function f returned None.

RE
let hMap = Belt.HashMap.String.make(~hintSize=10);
Belt.HashMap.String.set(hMap, "1", "value1");
Belt.HashMap.String.set(hMap, "2", "value2");

Belt.HashMap.String.keepMapInPlace(hMap, (key, value) => {
  key == "1" ? None : Some(value)
});

let size: t('a) => int;

size(tbl) returns the number of bindings in tbl. It takes constant time.

RE
let hMap = Belt.HashMap.String.make(~hintSize=10);
Belt.HashMap.String.set(hMap, "1", "value1");
Belt.HashMap.String.set(hMap, "2", "value2");

Belt.HashMap.String.size(hMap) == 2;

let toArray: t('a) => array((key, 'a));

Returns array of key value pairs.

RE
let hMap = Belt.HashMap.String.make(~hintSize=10);
Belt.HashMap.String.set(hMap, "1", "value1");
Belt.HashMap.String.set(hMap, "2", "value2");

Belt.HashMap.String.toArray(hMap) == [|("1", "value1"), ("2", "value2")|];

let keysToArray: t('a) => array(key);

Returns array of keys.

RE
let hMap = Belt.HashMap.String.make(~hintSize=10);
Belt.HashMap.String.set(hMap, "1", "value1");
Belt.HashMap.String.set(hMap, "2", "value2");

Belt.HashMap.String.keysToArray(hMap) == [|"1", "2"|];

let valuesToArray: t('a) => array('a);

Returns array of values.

RE
let hMap = Belt.HashMap.String.make(~hintSize=10);
Belt.HashMap.String.set(hMap, "1", "value1");
Belt.HashMap.String.set(hMap, "2", "value2");

Belt.HashMap.String.valuesToArray(hMap) == [|"value1", "value2"|];

let fromArray: array((key, 'a)) => t('a);

Creates new hash map from array of pairs.

Returns array of values.

RE
let hMap = Belt.HashMap.String.fromArray([|("1", "value1"), ("2", "value2")|]);
Belt.HashMap.String.toArray(hMap) == [|("1", "value1"), ("2", "value2")|];

let mergeMany: (t('a), array((key, 'a))) => unit;

Merges many key value pairs into hash map.

RE
let hMap = Belt.HashMap.String.make(~hintSize=10);
Belt.HashMap.String.mergeMany(hMap, [|("1", "value1"), ("2", "value2")|]);

let getBucketHistogram: t('a) => array(int);

RE
let hMap = Belt.HashMap.String.make(~hintSize=10);
Belt.HashMap.String.set(hMap, "1", "1");

Belt.HashMap.String.getBucketHistogram(hMap);

let logStats: t('a) => unit;

RE
let hMap = Belt.HashMap.String.make(~hintSize=10);
Belt.HashMap.String.set(hMap, "1", "1");

Belt.HashMap.String.logStats(hMap);