49ff4115b584abb6fd59e094b468686c2a1f919d
1 /* jshint bitwise:false */
4 var CONTROL_BUCKET
= 'control',
5 MAX_INT32_UNSIGNED
= 4294967295;
8 * An implementation of Jenkins' one-at-a-time hash.
10 * @see https://en.wikipedia.org/wiki/Jenkins_hash_function
12 * @param {string} string String to hash
13 * @return {number} The hash as a 32-bit unsigned integer
16 * @author Ori Livneh <ori@wikimedia.org>
17 * @see https://jsbin.com/kejewi/4/watch?js,console
19 function hashString( string
) {
24 hash
+= string
.charCodeAt( i
);
25 hash
+= ( hash
<< 10 );
26 hash
^= ( hash
>> 6 );
28 hash
+= ( hash
<< 3 );
29 hash
^= ( hash
>> 11 );
30 hash
+= ( hash
<< 15 );
36 * Provides an API for bucketing users in experiments.
38 * @class mw.experiments
44 * Gets the bucket for the experiment given the token.
46 * The name of the experiment and the token are hashed. The hash is converted
47 * to a number which is then used to get a bucket.
49 * Consider the following experiment specification:
53 * name: 'My first experiment',
63 * The experiment has three buckets: control, A, and B. The user has a 50%
64 * chance of being assigned to the control bucket, and a 25% chance of being
65 * assigned to either the A or B buckets. If the experiment were disabled,
66 * then the user would always be assigned to the control bucket.
68 * This function is based on the deprecated `mw.user.bucket` function.
70 * @param {Object} experiment
71 * @param {string} experiment.name The name of the experiment
72 * @param {boolean} experiment.enabled Whether or not the experiment is
73 * enabled. If the experiment is disabled, then the user is always assigned
74 * to the control bucket
75 * @param {Object} experiment.buckets A map of bucket name to probability
76 * that the user will be assigned to that bucket
77 * @param {string} token A token that uniquely identifies the user for the
78 * duration of the experiment
79 * @return {string} The bucket
81 getBucket: function ( experiment
, token
) {
82 var buckets
= experiment
.buckets
,
89 if ( !experiment
.enabled
|| $.isEmptyObject( experiment
.buckets
) ) {
90 return CONTROL_BUCKET
;
93 for ( key
in buckets
) {
94 range
+= buckets
[ key
];
97 hash
= hashString( experiment
.name
+ ':' + token
);
98 max
= ( hash
/ MAX_INT32_UNSIGNED
) * range
;
100 for ( key
in buckets
) {
101 acc
+= buckets
[ key
];
110 }( mediaWiki
, jQuery
) );