218 lines
6.1 KiB
Plaintext
218 lines
6.1 KiB
Plaintext
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{{alias}}( collection, [options,] indicator, done )
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Generates a frequency table according to an indicator function.
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The table is an array of arrays where each sub-array corresponds to a unique
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value in the input collection. Each sub-array is structured as follows:
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- 0: unique value
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- 1: value count
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- 2: frequency percentage
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When invoked, the indicator function is provided a maximum of four
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arguments:
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- `value`: collection value
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- `index`: collection index
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- `collection`: the input collection
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- `next`: a callback to be invoked after processing a collection `value`
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The actual number of provided arguments depends on function length. If the
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indicator function accepts two arguments, the indicator function is
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provided:
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- `value`
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- `next`
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If the indicator function accepts three arguments, the indicator function is
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provided:
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- `value`
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- `index`
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- `next`
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For every other indicator function signature, the indicator function is
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provided all four arguments.
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The `next` callback takes two arguments:
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- `error`: error argument
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- `group`: value group
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If an indicator function calls the `next` callback with a truthy `error`
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argument, the function suspends execution and immediately calls the `done`
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callback for subsequent `error` handling.
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If provided an empty collection, the function calls the `done` callback with
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an empty array as the second argument.
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Execution is *not* guaranteed to be asynchronous. To guarantee asynchrony,
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wrap the `done` callback in a function which either executes at the end of
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the current stack (e.g., `nextTick`) or during a subsequent turn of the
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event loop (e.g., `setImmediate`, `setTimeout`).
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The function does not support dynamic collection resizing.
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The function does not skip `undefined` elements.
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Parameters
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----------
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collection: Array|TypedArray|Object
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Input collection over which to iterate. If provided an object, the
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object must be array-like (excluding strings and functions).
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options: Object (optional)
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Function options.
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options.limit: integer (optional)
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Maximum number of pending invocations. Default: Infinity.
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options.series: boolean (optional)
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Boolean indicating whether to process each collection element
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sequentially. Default: false.
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options.thisArg: any (optional)
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Execution context.
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indicator: Function
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Indicator function specifying how to categorize a collection element.
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done: Function
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A callback invoked either upon processing all collection elements or
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upon encountering an error.
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Examples
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--------
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// Basic usage:
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> function indicator( value, index, next ) {
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... setTimeout( onTimeout, value );
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... function onTimeout() {
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... console.log( value );
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... next( null, ( index%2 === 0 ) ? 'even': 'odd' );
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... }
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... };
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> function done( error, result ) {
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... if ( error ) {
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... throw error;
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... }
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... console.log( result );
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... };
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> var arr = [ 3000, 2500, 1000, 750 ];
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> {{alias}}( arr, indicator, done )
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750
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1000
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2500
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3000
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[ [ 'odd', 2, 0.5 ], [ 'even', 2, 0.5 ] ]
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// Limit number of concurrent invocations:
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> function indicator( value, index, next ) {
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... setTimeout( onTimeout, value );
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... function onTimeout() {
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... console.log( value );
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... next( null, ( index%2 === 0 ) ? 'even' : 'odd' );
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... }
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... };
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> function done( error, result ) {
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... if ( error ) {
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... throw error;
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... }
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... console.log( result );
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... };
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> var opts = { 'limit': 2 };
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> var arr = [ 3000, 2500, 1000, 750 ];
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> {{alias}}( arr, opts, indicator, done )
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2500
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3000
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1000
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750
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[ [ 'odd', 2, 0.5 ], [ 'even', 2, 0.5 ] ]
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// Process sequentially:
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> function indicator( value, index, next ) {
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... setTimeout( onTimeout, value );
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... function onTimeout() {
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... console.log( value );
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... next( null, ( index%2 === 0 ) ? 'even' : 'odd' );
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... }
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... };
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> function done( error, result ) {
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... if ( error ) {
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... throw error;
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... }
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... console.log( result );
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... };
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> var opts = { 'series': true };
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> var arr = [ 3000, 2500, 1000, 750 ];
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> {{alias}}( arr, opts, indicator, done )
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3000
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2500
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1000
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750
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[ [ 'even', 2, 0.5 ], [ 'odd', 2, 0.5 ] ]
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{{alias}}.factory( [options,] indicator )
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Returns a function which generates a frequency table according to an
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indicator function.
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Parameters
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----------
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options: Object (optional)
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Function options.
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options.limit: integer (optional)
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Maximum number of pending invocations. Default: Infinity.
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options.series: boolean (optional)
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Boolean indicating whether to process each collection element
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sequentially. Default: false.
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options.thisArg: any (optional)
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Execution context.
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indicator: Function
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Indicator function specifying how to categorize a collection element.
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Returns
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-------
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out: Function
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A function which generates a frequency table according to an indicator
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function.
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Examples
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--------
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> function indicator( value, index, next ) {
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... setTimeout( onTimeout, value );
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... function onTimeout() {
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... console.log( value );
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... next( null, ( index%2 === 0 ) ? 'even' : 'odd' );
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... }
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... };
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> var opts = { 'series': true };
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> var f = {{alias}}.factory( opts, indicator );
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> function done( error, result ) {
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... if ( error ) {
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... throw error;
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... }
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... console.log( result );
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... };
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> var arr = [ 3000, 2500, 1000, 750 ];
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> f( arr, done )
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3000
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2500
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1000
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750
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[ [ 'even', 2, 0.5 ], [ 'odd', 2, 0.5 ] ]
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> arr = [ 2000, 1500, 1000, 750 ];
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> f( arr, done )
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2000
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1500
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1000
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750
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[ [ 'even', 2, 0.5 ], [ 'odd', 2, 0.5 ] ]
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See Also
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--------
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