190 lines
3.6 KiB
Markdown
190 lines
3.6 KiB
Markdown
<!--
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@license Apache-2.0
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Copyright (c) 2018 The Stdlib Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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-->
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# Try Function
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> Wrap a function in a try/catch block.
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<section class="usage">
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## Usage
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```javascript
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var wrap = require( '@stdlib/utils/try-function' );
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```
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#### wrap( fcn )
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Wraps a `function` in a `try/catch` block.
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```javascript
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function fcn() {
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throw new Error( 'beep boop' );
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}
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var f = wrap( fcn );
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var out = f();
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if ( out instanceof Error ) {
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console.error( out.message );
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// => 'beep boop'
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}
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```
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The returned `function` has the same signature as the wrapped `function`.
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```javascript
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function fcn( a, b, c, d ) {
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var sum = a + b + c + d;
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if ( sum < 10 ) {
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throw new Error( 'invalid arguments. Arguments must sum to a number greater than or equal to 10.' );
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}
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return sum;
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}
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var f = wrap( fcn );
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var out = f( 5, 6, 7, 8 );
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// returns 26
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out = f( 1, 2, 3, 1 );
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// returns <Error>
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```
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If provided an asynchronous `function`, the returned `function` only traps `errors` which occur during the current event loop tick.
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<!-- run throws: true -->
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```javascript
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function fcn( a, b, clbk ) {
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if ( !a ) {
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throw new Error( 'invalid argument.' );
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}
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setTimeout( onTimeout, 0 );
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function onTimeout() {
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if ( !b ) {
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throw new Error( 'invalid argument.' );
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}
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clbk();
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}
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}
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function done() {
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console.log( 'beep' );
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}
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var f = wrap( fcn );
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var out = f( null, 5, done );
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// returns <Error>
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out = f( true, null, done );
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// returns undefined
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```
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</section>
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<!-- /.usage -->
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<section class="notes">
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## Notes
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- Isolating `try/catch` blocks as separate wrapped `functions` prevents a parent scope from permanently entering optimization hell.
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- If a function throws a literal, the literal is serialized as a `string` and returned as an `Error` object.
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</section>
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<!-- /.notes -->
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<section class="examples">
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## Examples
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<!-- run throws: true -->
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<!-- eslint no-undef: "error" -->
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```javascript
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var wrap = require( '@stdlib/utils/try-function' );
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function beep( str ) {
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if ( typeof str !== 'string' ) {
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throw new TypeError( 'invalid argument. Must provide a string primitive. Value: `' + str + '`.' );
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}
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return 'beep ' + str;
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}
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function boop( str, clbk ) {
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if ( typeof str !== 'string' ) {
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throw new TypeError( 'invalid argument. Must provide a string primitive. Value: `' + str + '`.' );
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}
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setTimeout( done, 1000 );
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function done() {
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if ( str !== 'beep' ) {
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throw new Error( 'invalid argument. String must equal `beep`. Value: `' + str + '`.' );
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}
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clbk( str + ' boop' );
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}
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}
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function done( str ) {
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if ( str !== 'beep boop' ) {
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throw new Error( 'huh?' );
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}
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}
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var out;
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var f;
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// Synchronous...
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f = wrap( beep );
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out = f( 'boop' );
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console.log( out );
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// => 'beep boop'
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out = f( null );
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console.log( out.message );
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// => '...'
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// Asynchronous...
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f = wrap( boop );
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out = f( 'beep', done );
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console.log( out );
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// => undefined
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out = f( 'foo', done );
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console.log( out );
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// => undefined
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```
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</section>
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<!-- /.examples -->
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<section class="links">
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</section>
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<!-- /.links -->
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