task3 --提取字符串常量

length/src/index.js

 export class Length {
   value
   unit
-  // unitEnum = ['foot', 'yard', 'inch']
+  static FOOT = 'foot'
+  static YARD = 'yard'
+  static INCH = 'inch'
 
   constructor(val, uint) {
     this.value = val
@@ -10,33 +12,33 @@ export class Length {
 
   getVal() {
     return this.value
-  }
+  }  
 
   getUint() {
     return this.unit
   }
   parseTo(unitNode) {
     let unitLength = this
-    if (this.unit === 'yard') {
-      if (unitNode === 'f') {
+    if (this.unit === Length.YARD ) {
+      if (unitNode === Length.FOOT) {
         unitLength = new Length(this.value * 3, unitNode)
-      } else if (unitNode === 'inch') {
+      } else if (unitNode === Length.INCH) {
         unitLength = new Length(this.value * 36, unitNode)
       }
     }
 
-    if (this.unit === 'inch') {
-      if (unitNode === 'yard') {
+    if (this.unit === Length.INCH) {
+      if (unitNode === Length.YARD) {
         unitLength = new Length(this.value / 36, unitNode)
-      } else if (unitNode === 'f') {
+      } else if (unitNode === Length.FOOT) {
         unitLength = new Length(this.value / 12, unitNode)
       }
     }
 
-    if (this.unit === 'f') {
-      if (unitNode === 'yard') {
+    if (this.unit === Length.FOOT) {
+      if (unitNode === Length.YARD) {
         unitLength = new Length(this.value / 3, unitNode)
-      } else if (unitNode === 'inch') {
+      } else if (unitNode === Length.INCH) {
         unitLength = new Length(this.value * 12, unitNode)
       }
     }

length/src/index.test.js

@@ -2,65 +2,65 @@ import { Length } from './index'
 
 describe('Length', () => {
   it("should 1 'foot' equals 1 'foot'", () => {
-    const length = new Length(1, 'f')
+    const length = new Length(1, Length.FOOT)
 
     expect(length.getVal()).toEqual(1)
-    expect(length.getUint()).toEqual('f')
+    expect(length.getUint()).toEqual(Length.FOOT)
   })
 
   it("should 1 'foot' equals 12 inches", () => {
-    const result = new Length(1, 'f').parseTo('inch')
+    const result = new Length(1, Length.FOOT).parseTo(Length.INCH)
 
     expect(result.getVal()).toEqual(12)
-    expect(result.getUint()).toEqual('inch')
+    expect(result.getUint()).toEqual(Length.INCH)
   })
 
-  it("should 3 feet equals 1 'yard'", () => {
-    const result = new Length(3, 'f').parseTo('yard')
+  it("should 3 feet equals 1 Length.YARD", () => {
+    const result = new Length(3, Length.FOOT).parseTo(Length.YARD)
 
     expect(result.getVal()).toEqual(1)
-    expect(result.getUint()).toEqual('yard')
+    expect(result.getUint()).toEqual(Length.YARD)
   })
 
-  it("should 1 'yard' equals 3 feet", () => {
-    const result = new Length(1, 'yard').parseTo('f')
+  it("should 1 Length.YARD equals 3 feet", () => {
+    const result = new Length(1, Length.YARD).parseTo(Length.FOOT)
 
     expect(result.getVal()).toEqual(3)
-    expect(result.getUint()).toEqual('f')
+    expect(result.getUint()).toEqual(Length.FOOT)
   })
 
-  it("should 1 'yard' equals 36 inches", () => {
-    const result = new Length(1, 'yard').parseTo('inch')
+  it("should 1 Length.YARD equals 36 inches", () => {
+    const result = new Length(1, Length.YARD).parseTo(Length.INCH)
 
     expect(result.getVal()).toEqual(36)
-    expect(result.getUint()).toEqual('inch')
+    expect(result.getUint()).toEqual(Length.INCH)
   })
 
-  it("should 1 'yard' equals 1 'yard'", () => {
-    const result = new Length(1, 'yard').parseTo('yard')
+  it("should 1 Length.YARD equals 1 Length.YARD", () => {
+    const result = new Length(1, Length.YARD).parseTo(Length.YARD)
 
     expect(result.getVal()).toEqual(1)
-    expect(result.getUint()).toEqual('yard')
+    expect(result.getUint()).toEqual(Length.YARD)
   })
 
   it("should 12 inches equals 1 'foot'", () => {
-    const result = new Length(12, 'inch').parseTo('f')
+    const result = new Length(12, Length.INCH).parseTo(Length.FOOT)
 
     expect(result.getVal()).toEqual(1)
-    expect(result.getUint()).toEqual('f')
+    expect(result.getUint()).toEqual(Length.FOOT)
   })
 
-  it("should 36 inches equals 1 'yard'", () => {
-    const result = new Length(36, 'inch').parseTo('yard')
+  it("should 36 inches equals 1 yard", () => {
+    const result = new Length(36, Length.INCH).parseTo(Length.YARD)
 
     expect(result.getVal()).toEqual(1)
-    expect(result.getUint()).toEqual('yard')
+    expect(result.getUint()).toEqual(Length.YARD)
   })
 
-  it("should 1 inch equals 1 'inch'", () => {
-    const result = new Length(1, 'inch').parseTo('inch')
+  it("should 1 inch equals 1 inch", () => {
+    const result = new Length(1, Length.INCH).parseTo(Length.INCH)
 
     expect(result.getVal()).toEqual(1)
-    expect(result.getUint()).toEqual('inch')
+    expect(result.getUint()).toEqual(Length.INCH)
   })
 })