把已经的接口适配成所需要的接口
    image.png

    现有 API，用于画点

    1. let drawPoint = function(point){
    2.     process.stdout.write('.');
    3. }

    console.log = function (d){ process.stdout.write(d + ‘\n’); }; console.log() 是带换行的

    现需要一个画矩形的类

    1. class Point{
    2.   constructor(x, y){
    3.     this.x = x;
    4.     this.y = y;
    5.   }
    7.   toString(){
    8.     return `(${this.x}, ${this.y})`;
    9.   }
    10. }
    12. class Line{
    13.   constructor(start, end){
    14.     this.start = start;
    15.     this.end = end;
    16.   }
    18.   toString(){
    19.       return `${this.start.toString()} 到 ${this.end.toString()}`;
    20.   }
    21. }
    23. class VectorObject extends Array{
    25. }
    27. class VectorRectangle extends VectorObject{
    28.   constructor(x, y, width, height){
    29.     super();
    30.     this.push(new Line(new Point(x, y), new Point(x + width, y)));
    31.     this.push(new Line(new Point(x + width, y), new Point(x + width, y + height)));
    32.     this.push(new Line(new Point(x, y), new Point(x, y + height)));
    33.     this.push(new Line(new Point(x, y + height), new Point(x + width, y + height)));
    34.   }
    35. }
    37. let vectorObjects = [
    38.     new VectorRectangle(1, 1, 10, 10),
    39.   new VectorRectangle(5, 5, 20, 20)
    40. ]

    构造把点转为直线的构造器，一直是一组点所构成

    1. class LineToPointAdapter{
    2.   constructor(line){ 
    3.     this.hash = JSON.stringify(line).hashCode();
    5.     if(LineToPointAdapter.cache[this.hash]){
    6.         return 
    7.     }
    9.     let points = [];
    11.     console.log(`${LineToPointAdapter.count++}: 正在为从 ${line.toString} 的直线生成点（没有使用缓存）`);
    13.     let left = Math.min(line.start.x, line.end.x);
    14.     let right = Math.max(line.start.y, line.end.y);
    15.     let top = Math.max(line.start.y, line.end.y);
    16.     let bottom = Math.min(line.start.y, line.end.y);
    18.     if(right - left === 0){
    19.       for(let y = bottom, y <= top; y++){
    20.         points.push(new Point(left, y));
    21.       }
    22.     } else if (top - bottom === 0){
    23.       for(let x = left, x <= right; x++){
    24.         points.push(new Point(x, top));
    25.       }
    26.     }
    28.     LineToPointAdapter.cache[this.hash] = points;
    29.   } 
    31.   get items(){
    32.       return LineToPointAdapter.cache[this.hash];
    33.   }
    34. }
    35. LineToPointAdapter.count = 0;
    36. LineToPointAdapter.cache = {};
    38. let drawPoints = function(){
    39.   for(let vo of vectorObjects){
    40.     for(let line of vo){
    41.       let adapter = new LineToPointerAdapter(line);
    42.       adapter.items.forEach(drawPoint);
    43.     }
    44.   }
    45. }
    47. drawPoints();
    48. drawPoints();
    1. String.prototype.hashCode = function(){
    2.   if(Array.prototype.reduce){
    3.     return this.split("").reduce(function(a,b){
    4.       a=((a<<5)-a)+b.charCodeAt(0);
    5.       return a&a;
    6.     }, 0)
    7.   }
    8.   let hash = 0;
    9.   if(this.length ===0) return hash;
    10.   for(let i=0;i<this.length;i++){
    11.     count character = this.charCodeAt(i);
    12.     hash = ((hash<<5)-hash)+character;
    13.     hash = hash & hash;
    14.   }
    15.   return hash;
    16. }