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Replace JavaScript expressions with other expressions.

$ yarn add --dev babel-plugin-transform-replace-expressions

Input file:

constenv=process.env.NODE_ENV;typeofHello==="number";

.babelrc:

{"plugins": [    ["babel-plugin-transform-replace-expressions",      {"replace": {"process.env.NODE_ENV":"\"production\"","typeof Hello":"42"        }      }    ]  ]}

Output:

constenv="production";42==="number";

A conflict happens when two replacements have the same Babelabstract syntax tree representation. For example expressionstypeof A andtypeof (A) are formatted differently but have the same AST representation as far as the plugin is concerned. In those situations the default is to raise an error, and can be overwritten by setting the optionallowConflictingReplacements totrue.

You can also always give the replacements as an array of key-value pairs. WhenallowConflictingReplacements is set totrue thelast conflicting replacement gets selected.

{"plugins":[["babel-plugin-transform-replace-expressions",{"replace":[["typeof A","B"],["typeof (A)","C"]],"allowConflictingReplacements":true}]]}

• Replacements are only applied to expressions. Therefore replacingDEBUG withfalse inconst DEBUG = true does nothing, but forif (DEBUG) {} the result isif (false) {}.

• Onlyfull expressions count. You can't replaceenv inprocess.env.NODE_ENV, you have to replaceprocess.env, which is a proper expression in Babel AST.

• A replacement is only applied when the result is valid JavaScript. For example replacinga with2 in the following code:

  a=1;b=a;

  yields

  a=1;b=2;

This plugin is licensed under the MIT license. SeeLICENSE.