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2.1.109 • Public • Published

set-webpack-public-path plugin for webpack


npm install @microsoft/set-webpack-public-path-plugin --save-dev


This simple plugin sets the __webpack_public_path__ variable to a value specified in the arguments, optionally appended to the SystemJs baseURL property.


To use the plugin, add it to the plugins array of your Webpack config. For example:

import { SetPublicPathPlugin } from '@microsoft/set-webpack-public-path-plugin';
  plugins: [
    new SetPublicPathPlugin( /* webpackPublicPathOptions */ )


scriptName = { }

This parameter is an object that takes two properties: a string property name, and a boolean property isTokenized. The name property is a regular expression string that is applied to all script URLs on the page. The last directory of the URL that matches the regular expression is used as the public path. For example, if the name property is set to my\-bundle_?[a-zA-Z0-9-_]*\.js and a script's URL is, the public path will be set to

If the isTokenized paramter is set to true, the regular expression string in name is treated as a tokenized string. The supported tokens are [name] and [hash]. Instances of the [name] substring are replaced with the chunk's name, and instances of the [hash] substring are replaced with the chunk's rendered hash. The name is regular expression-escaped. For example, if the name property is set to [name]_?[a-zA-Z0-9-_]*\.js, isTokenized is set to true, and the chunk's name is my-bundle, and a script's URL is, the public path will be set to

This option is exclusive to other options. If it is set, systemJs, publicPath, and urlPrefix will be ignored.

systemJs = true

Use System.baseURL if it is defined.

publicPath = '...'

Use the specified path as the base public path. If urlPrefix is also defined, the public path will be the concatenation of the two (i.e. - __webpack_public_path__ = URL.concat({publicPath} + {urlPrefix}). This option takes precedence over the systemJs option.

urlPrefix = '...'

Use the specified string as a URL prefix after the SystemJS path or the publicPath option. If neither systemJs nor publicPath is defined, this option will not apply and an exception will be thrown.

regexVariable = '...'

Check for a variable with name ... on the page and use its value as a regular expression against script paths to the bundle's script. If a value foo is passed into regexVariable, the produced bundle will look for a variable called foo during initialization, and if a foo variable is found, use its value as a regular expression to detect the bundle's script.

For example, if the regexVariable option is set to scriptRegex and scriptName is set to { name: 'myscript' }, consider two cases:

Case 1
      var scriptRegex = /thescript/i;
    <script src="theScript.js"></script> 

In this case, because there is a scriptRegex variable defined on the page, the bundle will use its value (/thescript/i) to find the script.

Case 2
    <script src="myScript.js"></script> 

In this case, because there is not a scriptRegex variable defined on the page, the bundle will use the value passed into the scriptName option to find the script.

getPostProcessScript = (variableName) => { ... }

A function that returns a snippet of code that manipulates the variable with the name that's specified in the parameter. If this parameter isn't provided, no post-processing code is included. The variable must be modified in-place - the processed value should not be returned. This is useful when non-entry assets are deployed to a parent directory or subdirectory of the directory to which the entry assets are deployed.

For example, if this parameter is set to this function

getPostProcessScript = (variableName) => {
  return `${variableName} = ${variableName} + 'assets/';`;

the public path variable will have /assets/ appended to the found path.

Note that the existing value of the variable already ends in a slash (/).

preferLastFoundScript = false

If true, find the last script matching the regexVariable (if it is set). If false, find the first matching script. This can be useful if there are multiple scripts loaded in the DOM that match the regexVariable.

skipDetection = false

If true, always include the code snippet to detect the public path regardless of whether chunks or assets are present.

SystemJS Caveat

When modules are loaded with SystemJS (and with the , scriptLoad: true meta option) <script src="..."></script> tags are injected onto the page, evaludated and then immediately removed. This causes an issue because they are removed before webpack module code begins to execute, so the publicPath=... option won't work for modules loaded with SystemJS.

To circumvent this issue, a small bit of code is availble to that will maintain a global register of script paths that have been inserted onto the page. This code block should be appended to bundles that are expected to be loaded with SystemJS and use the publicPath=... option.


This function returns a block of JavaScript that maintains a global register of script tags. If the optional boolean parameter is set to true, the code is not minified. By default, it is minified. You can detect if the plugin may require the global register code by searching for the value of the registryVariableName field.

Usage without registryVariableName

var setWebpackPublicPath = require('@microsoft/set-webpack-public-path-plugin');
var gulpInsert = require('gulp-insert');

Usage with registryVariableName

var setWebpackPublicPath = require('@microsoft/set-webpack-public-path-plugin');
var gulpInsert = require('gulp-insert');
var gulpIf = require('gulp-if');
var detectRegistryVariableName = function (file) {
  return file.contents.toString().indexOf(setWebpackPublicPath.registryVariableName) !== -1;
  .pipe(gulpIf(detectRegistryVariableName, gulpInsert.append(setWebpackPublicPath.getGlobalRegisterCode(true))))






npm i @microsoft/set-webpack-public-path-plugin

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