canvas原生实现前端网页移动端签名

let c = document.getElementById("canvas")

let canvas = document.createElement("canvas")

let availHeight = document.documentElement.clientHeight

let off = availHeight - 400

canvas.height = '350'

canvas.width = c.clientWidth

c.appendChild(canvas)

let dr = canvas.getContext('2d')

dr.strokeStyle = 'blue'

canvas.addEventListener('touchstart',(e)=>{

  dr.beginPath()

  dr.moveTo(e.changedTouches["0"].pageX,e.changedTouches["0"].pageY-off)

})

canvas.addEventListener('touchmove',(e)=>{

  dr.lineTo(e.changedTouches[0].pageX, e.changedTouches[0].pageY-off)

  dr.stroke()

})

canvas.addEventListener('touchend',(e)=>{

  dr.closePath()

})