https://developers.weixin.qq.com/miniprogram/en/dev/api/canvas/wx.createOffscreenCanvas.html

Code:

    // Create Off Screen 2D canvas Example
    const canvas = wx.createOffscreenCanvas({type: '2d', width: 300, height: 150})
    // Obtain context。 Note that this must be consistent with the type Agreement
    const context = canvas.getContext('2d')
    
    console.log("====");
    console.log(context);

Output:

====
[sm]:61 undefined