JSTransform

Usage

Advanced API

varjstranform=require('jstransform')

jstransform.transform(visitors, code, options={})

jstransform.Syntax

Simple API

varsimple=require('jstransform/simple')

simple.transform(code, options={})

simple.transformFile(file, options={}, callback)

callback(err,result)

simple.transformFileSync(file, options={})

CLI

% jstransform --help  Usage: jstransform [options]<source directory><output directory> [<module ID> [<module ID> ...]]  Options:-h, --help                               output usage information    -V, --version                            output the version number-c, --config [file]                      JSON configuration file (no file or - means STDIN)-w, --watch                              Continually rebuild-x, --extension<js| coffee| ...>      File extension to assume when resolving module identifiers    --relativize                             Rewrite all module identifiers to be relative    --follow-requires                        Scan modulesfor required dependencies    --use-provides-module                    Respect @providesModules pragmain files    --cache-dir<directory>                  Alternate directory to usefor disk cache    --no-cache-dir                           Disable the disk cache    --source-charset<utf8| win1252| ...>  Charset ofsource (default: utf8)    --output-charset<utf8| win1252| ...>  Charset of output (default: utf8)    --react                                  Turns on the React JSX and React displayName transforms    --es6                                    Turns on available ES6 transforms    --es7                                    Turns on available ES7 transforms    --harmony                                Shorthand toenable all ES6 and ES7 transforms    --utility                                Turns on available utility transforms    --target [version]                       Specify your target version of ECMAScript. Valid values are"es3" and"es5". The default is"es5"."es3" will avoid uses of defineProperty and will quote reserved words. WARNING:"es5" is not properly supported, even with the use of es5shim, es5sham. If you need to support IE8, use"es3".    --strip-types                            Strips outtype annotations.    --es6module                              Parses the file as a valid ES6 module. (Note that this means implicit strict mode)    --non-strict-es6module                   Parses the file as an ES6 module, except disables implicit strict-mode. (This is usefulif you're porting non-ES6 modules to ES6, but haven't yet verified that they are strict-mode safe yet)    --source-map-inline                      Embed inline sourcemapin transformedsource    --source-filename                        Filename to use when generating the inline sourcemap. Will default to filename when processing files

Examples

Advanced API

Using a pre-bundled or existing transform:

/** * Reads a source file that may (or may not) contain ES6 classes, transforms it * to ES5 compatible code using the pre-bundled ES6 class visitors, and prints * out the result. */vares6ClassVisitors=require('jstransform/visitors/es6-class-visitors').visitorList;varfs=require('fs');varjstransform=require('jstransform');varoriginalFileContents=fs.readFileSync('path/to/original/file.js','utf-8');vartransformedFileData=jstransform.transform(es6ClassVisitors,originalFileContents);console.log(transformedFileData.code);

Using multiple pre-bundled or existing transforms at once:

/** * Reads a source file that may (or may not) contain ES6 classes *or* arrow * functions, transforms them to ES5 compatible code using the pre-bundled ES6 * visitors, and prints out the result. */vares6ArrowFuncVisitors=require('jstransform/visitors/es6-arrow-function-visitors').visitorList;vares6ClassVisitors=require('jstransform/visitors/es6-class-visitors').visitorList;varjstransform=require('jstransform');// Normally you'd read this from the filesystem, but I'll just use a string here// to simplify the example.varoriginalFileContents="var a = (param1) => param1; class FooClass {}";vartransformedFileData=jstransform.transform(es6ClassVisitors.concat(es6ArrowFuncVisitors),originalFileContents);// var a = function(param1)  {return param1;}; function FooClass(){"use strict";}console.log(transformedFileData.code);

Writing a simple custom transform:

/** * Creates a custom transformation visitor that prefixes all calls to the * `eval()` function with a call to `alert()` saying how much of a clown you are * for using eval. */varjstransform=require('jstransform');varutils=require('jstransform/src/utils');varSyntax=jstransform.Syntax;functionvisitEvalCallExpressions(traverse,node,path,state){// Appends an alert() call to the output buffer *before* the visited node// (in this case the eval call) is appended to the output bufferutils.append('alert("...eval?...really?...");',state);// Now we copy the eval expression to the output buffer from the original// sourceutils.catchup(node.range[1],state);}visitEvalCallExpressions.test=function(node,path,state){returnnode.type===Syntax.CallExpression&&node.callee.type===Syntax.Identifier&&node.callee.name==='eval';};// Normally you'd read this from the filesystem, but I'll just use a string here// to simplify the example.varoriginalFileContents="eval('foo');";vartransformedFileData=jstransform.transform([visitEvalCallExpressions],// Multiple visitors may be applied at once, so an// array is always expected for the first argumentoriginalFileContents);// alert("...eval?...really?...");eval('foo');console.log(transformedFileData.code);

Simple API

Reading a file and applying tranforms

varsimple=require('jstransform/simple');varfs=require('fs');varoriginalCode=fs.readFileSync('path/to/file.js');// Apply all available ES6 transformsvartransformed=simple.transform(originalCode,{es6:true});console.log(transformed.code);// Apply ES6 and ES7, generating ES3 compatible code (for IE8)transformed=simple.transform(originalCode,{harmony:true,target:'es3'});console.log(transformed.code);

Migration Guide

Simple API

CLI