1. BUG
1.1 BUG触发情况
在使用vis.js绘图时，加入两个节点A和B之间既存在一条从A指向B的边，同时也存在一条从B指向A的边，那么这个绘图库就会崩溃。
1.2 BUG解析
vis.js是动态计算两个节点之间位置的，然后将其在页面上展示出来，而在上述介绍的情况下，在计算A和B之间的距离时，代码中会出现除0的BUG，导致程序崩溃。
2. 解决方案
源码有3万多行，为了找这个BUG花了一周的时间，最终确定了出问题的函数。
在vis.js源码第12258行(版本更新后位置可能不同)，有个_calculateNodeForces()函数，源码如下：
/** * Calculate the forces the nodes apply on eachother based on a repulsion field. * This field is linearly approximated. * * @private */ _calculateNodeForces: function () { var dx, dy, angle, distance, fx, fy, combinedClusterSize, repulsingForce, node1, node2, i, j; var nodes = this.calculationNodes; var nodeIndices = this.calculationNodeIndices; // approximation constants var a_base = -2 / 3; var b = 4 / 3; // repulsing forces between nodes var nodeDistance = this.constants.physics.repulsion.nodeDistance; var minimumDistance = nodeDistance; // we loop from i over all but the last entree in the array // j loops from i+1 to the last. This way we do not double count any of the indices, nor i == j for (i = 0; i < nodeIndices.length - 1; i++) { node1 = nodes[nodeIndices[i]]; for (j = i + 1; j < nodeIndices.length; j++) { node2 = nodes[nodeIndices[j]]; combinedClusterSize = node1.clusterSize + node2.clusterSize - 2; dx = node2.x - node1.x; dy = node2.y - node1.y; distance = Math.sqrt(dx * dx + dy * dy); minimumDistance = (combinedClusterSize == 0) ? nodeDistance : (nodeDistance * (1 + combinedClusterSize * this.constants.clustering.distanceAmplification)); var a = a_base / minimumDistance; if (distance < 2 * minimumDistance) { if (distance < 0.5 * minimumDistance) { repulsingForce = 1.0; } else { repulsingForce = a * distance + b; // linear approx of 1 / (1 + Math.exp((distance / minimumDistance - 1) * steepness)) } // amplify the repulsion for clusters. repulsingForce *= (combinedClusterSize == 0) ? 1 : 1 + combinedClusterSize * this.constants.clustering.forceAmplification; repulsingForce = repulsingForce / distance; fx = dx * repulsingForce; fy = dy * repulsingForce; node1.fx -= fx; node1.fy -= fy; node2.fx += fx; node2.fy += fy; } } } } };
这里面有个distance变量，已标红，就是这个变量在我们介绍的情况下会为0，然后它又作为一个被除数，所以程序崩溃。
修改后的代码如下：
/** * Calculate the forces the nodes apply on eachother based on a repulsion field. * This field is linearly approximated. * * @private */ _calculateNodeForces: function () { var dx, dy, angle, distance, fx, fy, combinedClusterSize, repulsingForce, node1, node2, i, j; var nodes = this.calculationNodes; var nodeIndices = this.calculationNodeIndices; // approximation constants var a_base = -2 / 3; var b = 4 / 3; // repulsing forces between nodes var nodeDistance = this.constants.physics.repulsion.nodeDistance; var minimumDistance = nodeDistance; // we loop from i over all but the last entree in the array // j loops from i+1 to the last. This way we do not double count any of the indices, nor i == j for (i = 0; i < nodeIndices.length - 1; i++) { node1 = nodes[nodeIndices[i]]; for (j = i + 1; j < nodeIndices.length; j++) { node2 = nodes[nodeIndices[j]]; combinedClusterSize = node1.clusterSize + node2.clusterSize - 2; dx = node2.x - node1.x; dy = node2.y - node1.y; distance = Math.sqrt(dx * dx + dy * dy); if(distance == 0){ distance = 0.001; } minimumDistance = (combinedClusterSize == 0) ? nodeDistance : (nodeDistance * (1 + combinedClusterSize * this.constants.clustering.distanceAmplification)); var a = a_base / minimumDistance; if (distance < 2 * minimumDistance) { if (distance < 0.5 * minimumDistance) { repulsingForce = 1.0; } else { repulsingForce = a * distance + b; // linear approx of 1 / (1 + Math.exp((distance / minimumDistance - 1) * steepness)) } // amplify the repulsion for clusters. repulsingForce *= (combinedClusterSize == 0) ? 1 : 1 + combinedClusterSize * this.constants.clustering.forceAmplification; repulsingForce = repulsingForce / distance; fx = dx * repulsingForce; fy = dy * repulsingForce; node1.fx -= fx; node1.fy -= fy; node2.fx += fx; node2.fy += fy; } } } } };
加上一个判断让它不要为0即可。
