反序列化

canvas.loadFromJSON(string)

 const draw = (canvas) => {
    const str =
      '{"version":"5.3.0","objects":[{"type":"rect","version":"5.3.0","originX":"left","originY":"top","left":120,"top":20,"width":60,"height":40,"fill":"transparent","stroke":"blue","strokeWidth":1,"strokeDashArray":null,"strokeLineCap":"butt","strokeDashOffset":0,"strokeLineJoin":"miter","strokeUniform":false,"strokeMiterLimit":4,"scaleX":1,"scaleY":1,"angle":0,"flipX":false,"flipY":false,"opacity":1,"shadow":null,"visible":true,"backgroundColor":"","fillRule":"nonzero","paintFirst":"fill","globalCompositeOperation":"source-over","skewX":0,"skewY":0,"rx":0,"ry":0}]}'
      canvas.loadFromJSON(str)
  }