JChehe

function getHorizontalInfoThroughPixels (ctx) {
 const canvas = ctx.canvas
 const width = canvas.width
 const height = canvas.height
 const data = ctx.getImageData(0, 0, width, height).data
 let firstCol = 0
 let lastCol = 0
 let isFindLastCol = false
 let isFindFirstCol = false

JChehe

/* 
 * 实现思路：
 * 1. 创建一个栈
 * 2. 遍历字符串
 *   - 栈为空时，若 item 为左括号则入栈，右括号则 return false
 *   - item 为左括号就入栈   
 *   - item 为右括号时，stack 就 pop 出左括号，判断两者是否匹配
 *   - 若匹配则继续
 *   - 若不匹配则 return false
 */