前端js中Map取值问题，如下：

我在前端js中写
var Map = JSON.stringify(layer.p1);
console.log(Map);
页面得到：
{"type":"line","x1":429,"y1":135,"x2":374,"y2":182,"x3":432,"y3":220,"x4":559,"y4":306,"x5":605,"y5":191,"x6":458,"y6":100}
我该如何从数组中获得x，y的最大值与最小值？

var map = {"type":"line","x1":429,"y1":135,"x2":374,"y2":182,"x3":432,"y3":220,"x4":559,"y4":306,"x5":605,"y5":191,"x6":458,"y6":100};
var xmax = -Infinity;
var ymax = -Infinity;
var xmin = Infinity;
var ymin = Infinity;
for (var n in map) {
    if (n.charAt(0)=="x") {
        xmax = Math.max(map[n],xmax);
        xmin = Math.min(map[n],xmin);
    }
    if (n.charAt(0)=="y") {
        ymax = Math.max(map[n],ymax);
        ymin = Math.min(map[n],ymin);
    }
}
alert("xmax = "+xmax+", ymax = "+ymax+", xmin = "+xmin+", ymin = "+ymin);

var map = {"type":"line","x1":429,"y1":135,"x2":374,"y2":182,"x3":432,"y3":220,"x4":559,"y4":306,"x5":605,"y5":191,"x6":458,"y6":100};

var x_max = -999999; //X最大值
var x_min = 9999999999999; //X最小值
var y_max = -999999;//Y最大值
var y_min = 9999999999999; //Y最小值
for (var k in map) {
if (k.substr(0, 1) == 'x') {
if (x_max < map[k]) x_max = map[k];
if (x_min > map[k]) x_min = map[k];
}
if (k.substr(0, 1) == 'y') {
if (y_max < map[k]) y_max = map[k];
if (y_min > map[k]) y_min = map[k];
}
}

 var x = { Map.x1, Map.x2, ... Map.x6 };
var y = { Map.y1, Map.y2, ... Map.y6 };
var max = x[0];
for (var i = 1; i < 6; i++)
if (max < x[i]) max = x[i];
alert("x的最大值" + max);
var max = y[0];
for (var i = 1; i < 6; i++)
if (max < y[i]) max = y[i];
alert("y的最大值" + max);

var maxx=0,maxy=0,minx=9999,miny=9999;
for(var i = 1; i<=6;i++){
var x=Map["x"+i];
var y=Map["y"+i];
if(x>maxx)
maxx = x;
else if(x minx = x;
if(y>maxy)
maxy = y;
else if(y<miny)
miny = y;
}

let data = {"type":"line","x1":429,"y1":135,"x2":374,"y2":182,"x3":432,"y3":220,"x4":559,"y4":306,"x5":605,"y5":191,"x6":458,"y6":100}

let xArray = []
let yArray = []
Object.keys(data).forEach(function(key){
if(key.match(/^x\d+/)){
xArray.push(data[key])
}
if(key.match(/^y\d+/)){
yArray.push(data[key])
}
})
let xMax = Math.max.apply(null,xArray)
let yMax = Math.max.apply(null,yArray)
let xMin = Math.min.apply(null,xArray)
let yMin = Math.min.apply(null,yArray)

var obj ={"type":"line","x1":429,"y1":135,"x2":374,"y2":182,"x3":432,"y3":220,"x4":559,"y4":306,"x5":605,"y5":191,"x6":458,"y6":100}

let arrX = []
let arrY = []
for (var key in obj) {
    console.log(typeof(obj[key]))
    if(typeof(obj[key]) === 'number'){
        if(key.indexOf('x') > -1) {
            arrX.push(obj[key])
        }
        if(key.indexOf('y') > -1) {
            arrY.push(obj[key])
        }
    }

}

console.log(arrX, arrY)

// es6
console.log('x最大值：' + Math.max(...arrX), 'x最小值：' + Math.min(...arrX))
console.log('y最大值：' + Math.max(...arrY), 'y最小值：' + Math.min(...arrY))

//es5 请使用下面的方法
// Math.max.apply(null,arrX)

望采纳