Javascript 从画布中的JSON加载而不清除

我想从JSON字符串在现有画布中添加对象，而不清除现有对象。但当我点击按钮添加时，它会清除我的画布，然后从json字符串添加。 请帮帮我怎么做？ 下面是我尝试过的

var yourData = '[{"type":"group","originX":"center","originY":"center","left":161.82,"top":76.48,"width":174.38,"height":59.05,"fill":"rgb(0,0,0)","stroke":null,"strokeWidth":1,"strokeDashArray":null,"strokeLineCap":"butt","strokeLineJoin":"miter","strokeMiterLimit":10,"scaleX":1,"scaleY":1,"angle":0,"flipX":false,"flipY":false,"opacity":1,"shadow":null,"visible":true,"clipTo":null,"backgroundColor":"","objects":[{"type":"line","originX":"center","originY":"center","left":0,"top":-0.01,"width":172.38,"height":1,"fill":"transparent","stroke":"transparent","strokeWidth":2,"strokeDashArray":null,"strokeLineCap":"butt","strokeLineJoin":"miter","strokeMiterLimit":10,"scaleX":1,"scaleY":1,"angle":0,"flipX":false,"flipY":false,"opacity":1,"shadow":null,"visible":true,"clipTo":null,"backgroundColor":"","x1":75.6300048828125,"y1":75.98500061035156,"x2":248.00997924804687,"y2":75.98500061035156},{"type":"rect","originX":"left","originY":"top","left":-86.19,"top":-30.03,"width":172.38,"height":59.05,"fill":"yellow","stroke":"red","strokeWidth":1,"strokeDashArray":null,"strokeLineCap":"butt","strokeLineJoin":"miter","strokeMiterLimit":10,"scaleX":1,"scaleY":1,"angle":0,"flipX":false,"flipY":false,"opacity":0.3,"shadow":null,"visible":true,"clipTo":null,"backgroundColor":"","rx":0,"ry":0,"x":0,"y":0}]}]';
var json = '{"objects":' + yourData + '}';

canvas.loadFromJSON(json, canvas.renderAll.bind(canvas), function(o, object) {
  fabric.log(o, object);
});

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画布元素上没有“loadFromJSON”方法，但它可以工作……唯一的事情是清除整个画布，然后添加jsonstring@JohnWick，下次，请记住直接在问题中包含您使用的库（我通过在此处包含正确的标记完成了此操作）。可能的重复我下次会记得…除了我们可以使用的loadFromJSON之外，画布元素上没有“loadFromJSON”方法。但它的工作…唯一的事情是清除整个画布，然后添加jsonstring@JohnWick，下次，请记住直接在问题中包含您使用的库（我已经在这里添加了正确的标记）下一次我会记住的可能的副本…除了loadFromJSON之外，我们可以使用什么