feat: add units to config

README.md

@@ -61,6 +61,7 @@ Type: `Object | Null`
 Default:
 ```js
 {
+    units: 'rem',
     rootValue: 16,
     unitPrecision: 5,
     propList: ['font', 'font-size', 'line-height', 'letter-spacing'],
@@ -72,6 +73,7 @@ Default:
 }
 ```
 
+- `rem` (String) Convert target unit.
 - `rootValue` (Number | Function) Represents the root element font size or returns the root element font size based on the [`input`](https://api.postcss.org/Input.html) parameter
 - `unitPrecision` (Number) The decimal numbers to allow the REM units to grow to.
 - `propList` (Array) The properties that can change from px to rem.

index.js

@@ -3,6 +3,7 @@ const filterPropList = require("./lib/filter-prop-list");
 const type = require("./lib/type");
 
 const defaults = {
+  units: 'rem',
   rootValue: 16,
   unitPrecision: 5,
   selectorBlackList: [],
@@ -43,13 +44,13 @@ function convertLegacyOptions(options) {
   });
 }
 
-function createPxReplace(rootValue, unitPrecision, minPixelValue) {
+function createPxReplace(rootValue, unitPrecision, minPixelValue, units) {
   return (m, $1) => {
     if (!$1) return m;
     const pixels = parseFloat($1);
     if (pixels < minPixelValue) return m;
     const fixedVal = toFixed(pixels / rootValue, unitPrecision);
-    return fixedVal === 0 ? "0" : fixedVal + "rem";
+    return fixedVal === 0 ? "0" : fixedVal + units;
   };
 }
 
@@ -145,7 +146,8 @@ module.exports = (options = {}) => {
       pxReplace = createPxReplace(
         rootValue,
         opts.unitPrecision,
-        opts.minPixelValue
+        opts.minPixelValue,
+        opts.units
       );
     },
     Declaration(decl) {

spec/pxtorem-spec.js

@@ -217,6 +217,19 @@ describe("unitPrecision", function() {
   });
 });
 
+describe("units", function() {
+  it("should replace with specified unit", function() {
+    var expected = ".rule { font-size: 0.938em }";
+    var options = {
+      unitPrecision: 3,
+      units: 'em'
+    };
+    var processed = postcss(pxtorem(options)).process(basicCSS).css;
+
+    expect(processed).toBe(expected);
+  });
+});
+
 describe("propWhiteList", function() {
   // Deprecate
   it("should only replace properties in the white list - legacy", function() {