微信小程序报错Error: Only digits (0-9) can be put inside [] in the path string: form_data[activity_name]

 这样写就报错了

formChanged(e) {
		let name = e.currentTarget.dataset.name || '';
		let key = 'form_data' + '[' + name + ']';
		let value =  e.detail.value;
		this.setData({
			[key]: value
		})
		console.log(this.data.form_data)
},

 下面修改了方法：

formChanged(e) {
		let name = e.currentTarget.dataset.name || '';
		let value =  e.detail.value;
		
		this.setData({
			[`form_data.${name}`]: value
		})
		console.log(this.data.form_data)
	},

这个就解决了