Merge pull request #149 from brikou/fix_modularScale_helper

fix(helpers): Fix modularScale computation, allow steps to be zero
styled-components · Apr 16, 2017 · 496c384 · 496c384
2 parents 79a1353 + d4aff94
commit 496c384
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Showing 3 changed files with 16 additions and 2 deletions.
diff --git a/src/helpers/modularScale.js b/src/helpers/modularScale.js
@@ -65,7 +65,7 @@ type Ratio =
  * }
  */
 function modularScale(steps: number, base?: number|string = '1em', ratio?: Ratio = 'perfectFourth') {
-  if (!steps) {
+  if (typeof steps !== 'number') {
     throw new Error('Please provide a number of steps to the modularScale helper.')
   }
   if (typeof ratio === 'string' && !ratioNames[ratio]) {
@@ -79,7 +79,7 @@ function modularScale(steps: number, base?: number|string = '1em', ratio?: Ratio
     throw new Error(`Invalid value passed as base to modularScale, expected number or em string but got "${base}"`)
   }
 
-  return `${realBase * realRatio * steps}em`
+  return `${realBase * (realRatio ** steps)}em`
 }
 
 export { ratioNames }

diff --git a/src/helpers/test/__snapshots__/modularScale.test.js.snap b/src/helpers/test/__snapshots__/modularScale.test.js.snap
@@ -117,3 +117,15 @@ Object {
   "font-size": "1.333em",
 }
 `;
+
+exports[`modularScale should use perfect fourth and 1em base by default 2`] = `
+Object {
+  "font-size": "1.776889em",
+}
+`;
+
+exports[`modularScale should use perfect fourth and 1em base by default 3`] = `
+Object {
+  "font-size": "1em",
+}
+`;
diff --git a/src/helpers/test/modularScale.test.js b/src/helpers/test/modularScale.test.js
@@ -9,6 +9,8 @@ describe('modularScale', () => {
 
   it('should use perfect fourth and 1em base by default', () => {
     expect({ 'font-size': modularScale(1) }).toMatchSnapshot()
+    expect({ 'font-size': modularScale(2) }).toMatchSnapshot()
+    expect({ 'font-size': modularScale(0) }).toMatchSnapshot()
   })
 
   it('should allow adjusting the base', () => {