//顶点着色器程序
    var VSHADER_SOURCE =
        "attribute vec4 a_Position;" +
        "attribute vec4 a_Color;" +
        "varying vec4 v_Color;" +
        "void main(){" +
        "gl_Position = a_Position;" +
        "v_Color = a_Color;" +
         "}";

    //片元着色器
    var FSHADER_SOURCE =
        "precision mediump float;" +
        "varying vec4 v_Color;" +
         "void main() {" +
         "gl_FragColor = v_Color;" +
         "}";

function initBuffers(gl,shaderProgram) {
  //顶点坐标和颜色
    var vertices = new Float32Array([
        0.0, 0.5, 1.0, 0.0, 0.0,
       -0.5, -0.5, 0.0, 1.0, 0.0,
        0.5, -0.5, 0.0, 0.0, 1.0,
    ]);
    var n = 3;//点的个数
    //创建缓冲区对象
    var vertexBuffer = gl.createBuffer();

    //将缓冲区对象绑定到目标
    gl.bindBuffer(gl.ARRAY_BUFFER,vertexBuffer);
    //向缓冲区写入数据
    gl.bufferData(gl.ARRAY_BUFFER,vertices,gl.STATIC_DRAW);
    //获取单个字节
    var FSIZE = vertices.BYTES_PER_ELEMENT;

    //获取坐标点
    var a_Positi
on = gl.getAttribLocation(shaderProgram, 'a_Position');
    //将缓冲区对象分配给a_Position变量
    gl.vertexAttribPointer(a_Position, 2, gl.FLOAT, false, FSIZE*5, 0);
    //连接a_Position变量与分配给它的缓冲区对象
    gl.enableVertexAttribArray(a_Position);


    //获取Color坐标点
    var a_Color = gl.getAttribLocation(shaderProgram, 'a_Color');
    //将缓冲区对象分配给a_Position变量
    gl.vertexAttribPointer(a_Color, 3, gl.FLOAT, false, FSIZE*5, FSIZE*2);
    //连接a_Position变量与分配给它的缓冲区对象
    gl.enableVertexAttribArray(a_Color);
    return n;
}

 var n = initBuffers(gl,shaderProgram);

    if(n<0){
        console.log('Failed to set the positions');
        return;
    }
    // 清除指定<画布>的颜色
    gl.clearColor(0.0, 0.0, 0.0, 1.0);

    // 清空 <canvas>
    gl.clear(gl.COLOR_BUFFER_BIT);

    gl.drawArrays(gl.TRIANGLES, 0, n);