157 lines
3.2 KiB
Markdown
157 lines
3.2 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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# trythen
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> If a function does not throw, return the function return value; otherwise, return the return value of a second function.
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<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->
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<section class="intro">
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</section>
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<!-- /.intro -->
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<!-- Package usage documentation. -->
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<section class="usage">
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## Usage
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```javascript
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var trythen = require( '@stdlib/utils/try-then' );
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```
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#### trythen( x, y )
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If a function `x` does not throw, returns the return value of `x`; otherwise, returns the return value of a second function `y`.
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```javascript
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function x1() {
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return 1.0;
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}
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function x2() {
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throw new Error( 'beep' );
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}
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function y() {
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return -1.0;
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}
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var z = trythen( x1, y );
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// returns 1.0
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z = trythen( x2, y );
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// returns -1.0
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```
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The function `y` is provided a single argument:
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- `error`: the error thrown by `x`
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```javascript
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var randu = require( '@stdlib/random/base/randu' );
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function x() {
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if ( randu() < 0.5 ) {
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throw new Error( 'beep' );
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}
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throw new TypeError( 'boop' );
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}
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function y( err ) {
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if ( err instanceof TypeError ) {
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return 'boops';
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}
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return 'beeps';
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}
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var z = trythen( x, y );
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// returns <string>
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```
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</section>
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<!-- /.usage -->
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<!-- Package usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
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<section class="notes">
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</section>
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<!-- /.notes -->
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<!-- Package usage examples. -->
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<section class="examples">
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## Examples
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<!-- eslint no-undef: "error" -->
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```javascript
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var randu = require( '@stdlib/random/base/randu' );
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var ceil = require( '@stdlib/math/base/special/ceil' );
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var repeatString = require( '@stdlib/string/repeat' );
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var trythen = require( '@stdlib/utils/try-then' );
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var z;
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var i;
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function x() {
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if ( randu() < 0.9 ) {
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throw new Error( 'BOOP' );
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}
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return repeatString( 'BOOP', ceil( randu()*3.0 ) );
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}
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function y() {
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return repeatString( 'beep', ceil( randu()*5.0 ) );
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}
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for ( i = 0; i < 100; i++ ) {
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z = trythen( x, y );
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console.log( z );
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}
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```
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</section>
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<!-- /.examples -->
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<!-- Section to include cited references. If references are included, add a horizontal rule *before* the section. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
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<section class="references">
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</section>
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<!-- /.references -->
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<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
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<section class="links">
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</section>
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<!-- /.links -->
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