task6--提取函数final

length/src/index.js

-import * as Constants from './constants'
+import { Constants } from './constants'
 export class Length {
   value
   unit
@@ -17,32 +17,67 @@ export class Length {
   }
   parseTo(unitNode) {
     let unitLength = this
-    if (this.unit === Constants.Constants.YARD) {
-      if (unitNode === Constants.Constants.FOOT) {
+    if (this.unit === Constants.YARD) {
+      if (unitNode === Constants.FOOT) {
         unitLength = new Length(this.multipleValue(3), unitNode)
-      } else if (unitNode === Constants.Constants.INCH) {
+      } else if (unitNode === Constants.INCH) {
         unitLength = new Length(this.multipleValue(36), unitNode)
       }
     }
 
-    if (this.unit === Constants.Constants.INCH) {
-      if (unitNode === Constants.Constants.YARD) {
+    if (this.unit === Constants.INCH) {
+      if (unitNode === Constants.YARD) {
         unitLength = new Length(this.divisionValue(36), unitNode)
-      } else if (unitNode === Constants.Constants.FOOT) {
+      } else if (unitNode === Constants.FOOT) {
         unitLength = new Length(this.value / 12, unitNode)
       }
     }
 
-    if (this.unit === Constants.Constants.FOOT) {
-      if (unitNode === Constants.Constants.YARD) {
+    if (this.unit === Constants.FOOT) {
+      if (unitNode === Constants.YARD) {
         unitLength = new Length(this.divisionValue(3), unitNode)
-      } else if (unitNode === Constants.Constants.INCH) {
+      } else if (unitNode === Constants.INCH) {
         unitLength = new Length(this.multipleValue(12), unitNode)
       }
     }
-
+    
     return unitLength
   }
+  as(targetUnit) {
+    return new Length(this._valueIn(targetUnit), targetUnit)
+  }
+  _valueIn(unit) {
+    if(this.unit === Constants.YARD) {
+      if(unit === Constants.FOOT) {
+        // this.multipleValue(3)
+        return this.value * 3
+      }
+      if(unit === Constants.INCH) {
+        // this.multipleValue(36)
+        return this.value * 36
+      }
+    }
+    if(this.unit === Constants.INCH) {
+      if(unit === Constants.YARD) {
+        // this.divisionValue(3)
+        return this.value / 36
+      }
+      if(unit ===Constants.FOOT) {
+        // this.divisionValue(12)
+        return this.value / 12
+      }
+    }
+    if(this.unit === Constants.FOOT) {
+      if(unit === Constants.YARD) {
+        // this.divisionValue(3)
+        return this.value / 3
+      }
+      if(unit === Constants.INCH) {
+        // this.multipleValue(12)
+        return this.value * 12
+      }
+    }
+  }
 
   divisionValue(conversion_Target_Unit_Value) {
     return this.value / conversion_Target_Unit_Value

length/src/index.test.js

@@ -10,56 +10,56 @@ describe('Length', () => {
   })
 
   it("should 1 'foot' equals 12 inches", () => {
-    const result = new Length(1, Constants.FOOT).parseTo(Constants.INCH)
+    const result = new Length(1, Constants.FOOT).as(Constants.INCH)// parseTo(Constants.INCH)
 
     expect(result.getVal()).toEqual(12)
     expect(result.getUint()).toEqual(Constants.INCH)
   })
 
   it("should 3 feet equals 1 yard", () => {
-    const result = new Length(3, Constants.FOOT).parseTo(Constants.YARD)
+    const result = new Length(3, Constants.FOOT).as(Constants.YARD)// parseTo(Constants.YARD)
 
     expect(result.getVal()).toEqual(1)
     expect(result.getUint()).toEqual(Constants.YARD)
   })
 
   it("should 1 Constants.YARD equals 3 feet", () => {
-    const result = new Length(1, Constants.YARD).parseTo(Constants.FOOT)
-
+    const result = new Length(1, Constants.YARD).as(Constants.FOOT) //parseTo(Constants.FOOT)
+ 
     expect(result.getVal()).toEqual(3)
     expect(result.getUint()).toEqual(Constants.FOOT)
   })
 
   it("should 1 Constants.YARD equals 36 inches", () => {
-    const result = new Length(1, Constants.YARD).parseTo(Constants.INCH)
+    const result = new Length(1, Constants.YARD).as(Constants.INCH)
 
     expect(result.getVal()).toEqual(36)
     expect(result.getUint()).toEqual(Constants.INCH)
   })
 
   it("should 1 Constants.YARD equals 1 Constants.YARD", () => {
-    const result = new Length(1, Constants.YARD).parseTo(Constants.YARD)
+    const result = new Length(1, Constants.YARD)
 
     expect(result.getVal()).toEqual(1)
     expect(result.getUint()).toEqual(Constants.YARD)
   })
 
   it("should 12 inches equals 1 'foot'", () => {
-    const result = new Length(12, Constants.INCH).parseTo(Constants.FOOT)
+    const result = new Length(12, Constants.INCH).as(Constants.FOOT)
 
     expect(result.getVal()).toEqual(1)
     expect(result.getUint()).toEqual(Constants.FOOT)
   })
 
   it("should 36 inches equals 1 yard", () => {
-    const result = new Length(36, Constants.INCH).parseTo(Constants.YARD)
+    const result = new Length(36, Constants.INCH).as(Constants.YARD)
 
     expect(result.getVal()).toEqual(1)
     expect(result.getUint()).toEqual(Constants.YARD)
   })
 
   it("should 1 inch equals 1 inch", () => {
-    const result = new Length(1, Constants.INCH).parseTo(Constants.INCH)
+    const result = new Length(1, Constants.INCH)
 
     expect(result.getVal()).toEqual(1)
     expect(result.getUint()).toEqual(Constants.INCH)