non-max-suppression.js

  nonMaxSuppression: function(scores, boxes) {
    const self = this

    let zipped = []
    for (let i = 0; i < scores.length; i++) {
      zipped.push([
        scores[i], [boxes[4*i], boxes[4*i + 1], boxes[4*i + 2], boxes[4*i + 3]], i
      ])
    }

    // sort by score
    const sorted = zipped.sort((a, b) => b[0] - a[0])
    const selected = []
    sorted.forEach(box => {
      let toAdd = true
      for (let i = 0; i < selected.length; i++) {
        const iou = self.box_iou(box[1], selected[i][1])
        if (iou > 0.5) {
          toAdd = false
        }
      }

      if (toAdd) {
        selected.push(box)
      }
    })

    return selected
  },

Hi syshen,
In your file, you have self.box_iou(), but you haven't instantiated this part.
Do you have in you possession the following please ?

I would suspect that box_iou is related to calculating the overlap, you can use a library like this: https://www.npmjs.com/package/rectangle-overlap

Very good example!