我的Javascript代码抛出此错误：“未捕获的TypeError：无法读取未定义的属性'0'”。我一直在搜索此错误，它似乎总是导致返回未定义的变量，但是我的代码似乎并非如此。当我通过Chrome的调试器运行它时，它表明我的所有变量都是在引发错误的行上定义的。首先使用参数constructor调用我班上的(64, -0.5, 0.5, -0.5, 0.5)。在constructor中，调用generateTriangles()，通过将12675个浮点值压入this.vBuffer来填充constructor。然后diamond_square()呼叫getVertex()，后者呼叫getVertex()。该错误引发到vBuffer的第二行。引发错误时，调试器显示vid填充了值，并且[vid]为0。它特别用红色下划线diamond_square()并将其链接到错误。无需调用constructor中的/** Class implementing 3D terrain. */
class Terrain{
/**
* Initialize members of a Terrain object
* @param {number} div Number of triangles along x axis and y axis
* @param {number} minX Minimum X coordinate value
* @param {number} maxX Maximum X coordinate value
* @param {number} minY Minimum Y coordinate value
* @param {number} maxY Maximum Y coordinate value
*/
constructor(div,minX,maxX,minY,maxY){
this.div = div;
this.minX=minX;
this.minY=minY;
this.maxX=maxX;
this.maxY=maxY;
// Allocate vertex array
this.vBuffer = [];
// Allocate triangle array
this.fBuffer = [];
// Allocate normal array
this.nBuffer = [];
// Allocate array for edges so we can draw wireframe
this.eBuffer = [];
console.log("Terrain: Allocated buffers");
this.generateTriangles();
console.log("Terrain: Generated triangles");
this.diamond_square();
console.log("Terrain: Performed Diamond-Square");
this.generateLines();
console.log("Terrain: Generated lines");
// Get extension for 4 byte integer indices for drwElements
var ext = gl.getExtension('OES_element_index_uint');
if (ext ==null){
alert("OES_element_index_uint is unsupported by your browser and terrain generation cannot proceed.");
}
}
/**
* Set the x,y,z coords of a vertex at location(i,j)
* @param {Object} v an an array of length 3 holding x,y,z coordinates
* @param {number} i the ith row of vertices
* @param {number} j the jth column of vertices
*/
setVertex(v,i,j)
{
var vid = 3*(i*(this.div+1) + j);
this.vbuffer[vid] = v[0];
this.vbuffer[vid+1] = v[1];
this.vbuffer[vid+2] = v[2];
}
/**
* Return the x,y,z coordinates of a vertex at location (i,j)
* @param {Object} v an an array of length 3 holding x,y,z coordinates
* @param {number} i the ith row of vertices
* @param {number} j the jth column of vertices
*/
getVertex(v,i,j)
{
var vid = 3*(i*(this.div+1) + j);
v[0] = this.vbuffer[vid];
v[1] = this.vbuffer[vid+1];
v[2] = this.vbuffer[vid+2];
}
/**
* Fill the vertex and buffer arrays
*/
generateTriangles()
{
var x_amount = (this.maxX - this.minX) / this.div;
var y_amount = (this.maxY - this.minY) / this.div;
for (var i = 0; i <= this.div; i++) {
for (var j = 0; j <= this.div; j++) {
this.vBuffer.push(j*x_amount + this.minX);
this.vBuffer.push(this.minY + i*y_amount);
this.vBuffer.push(0);
this.nBuffer.push(0);
this.nBuffer.push(0);
this.nBuffer.push(1);
}
}
for (var i = 0; i < this.div; i++) {
for (var j = 0; j < this.div; j++) {
var vid = i*(this.div+1) + j;
this.fBuffer.push(vid);
this.fBuffer.push(vid + this.div+1);
this.fBuffer.push(vid + this.div+2);
this.fBuffer.push(vid);
this.fBuffer.push(vid+1);
this.fBuffer.push(vid + this.div+2);
}
}
this.numVertices = this.vBuffer.length/3;
this.numFaces = this.fBuffer.length/3;
}
diamond_square()
{
// initialize corners to 0
var init_value = 0;
var max = this.div;
var v = [0.0, 0.0, 0.0];
// top-left corner
this.getVertex(v, 0, 0);
v[2] = init_value;
this.setVertex(v, 0, 0);
// bottom-left corner
this.getVertex(v, 0, max);
v[2] = init_value;
this.setVertex(v, 0, max);
// top-right corner
this.getVertex(v, max, 0);
v[2] = init_value;
this.setVertex(v, max, 0);
// bottom-right corner
this.getVertex(v, max, max);
v[2] = init_value;
this.setVertex(v, max, max);
// perform diamond-square recursively on the rest of the vertices
this.subsection(max);
}
}
，此代码即可完美运行。这是相关代码：
empid DT
9999 2018-10-23 19:00:00.000
9999 2018-10-24 07:00:00.000
9999 2018-10-21 08:00:00.000
9999 2018-10-22 06:00:00.000
9999 2018-10-24 03:00:00.000
9999 2018-10-24 05:00:00.000
9999 2018-10-23 06:00:00.000
9999 2018-10-23 21:00:00.000
答案 0 :(得分：1)
在您误拼了getVertex的{{1}}和setVertex函数中，您使用了实际上未定义的this.vBuffer，这引发了异常
this.vbuffer