refactor: Drop.prototype.value => valueOf

src/drop/blank-drop.ts

@@ -5,7 +5,7 @@ import { EmptyDrop } from '../drop/empty-drop'
 export class BlankDrop extends EmptyDrop {
   equals (value: any) {
     if (value === false) return true
-    if (isNil(isDrop(value) ? value.value() : value)) return true
+    if (isNil(isDrop(value) ? value.valueOf() : value)) return true
     if (isString(value)) return /^\s*$/.test(value)
     return super.equals(value)
   }

src/drop/empty-drop.ts

@@ -21,7 +21,7 @@ export class EmptyDrop extends Drop implements IDrop, IComparable {
   leq () {
     return false
   }
-  value () {
+  valueOf () {
     return ''
   }
 }

src/drop/idrop.ts

@@ -2,9 +2,9 @@ import { Drop } from './drop'
 import { isFunction } from '../util/underscore'
 
 export interface IDrop {
-  value(): any
+  valueOf(): any
 }
 
 export function isDrop (value: any): value is IDrop {
-  return value instanceof Drop && isFunction((value as any).value)
+  return value instanceof Drop && isFunction((value as any).valueOf)
 }

src/drop/null-drop.ts

@@ -6,7 +6,7 @@ import { BlankDrop } from '../drop/blank-drop'
 
 export class NullDrop extends Drop implements IDrop, IComparable {
   equals (value: any) {
-    return isNil(isDrop(value) ? value.value() : value) || value instanceof BlankDrop
+    return isNil(isDrop(value) ? value.valueOf() : value) || value instanceof BlankDrop
   }
   gt () {
     return false
@@ -20,7 +20,7 @@ export class NullDrop extends Drop implements IDrop, IComparable {
   leq () {
     return false
   }
-  value () {
+  valueOf () {
     return null
   }
 }