Typescript: typescript operator '+=' cannot be applied to types Number and Number

[Akxe]

Why?

ref: [
  {
    value: Number
    date?: Date
  }
]
total() {
  var total = 0
  for (var ind = this.ref.length - 1; ind >= 0; ind--) {
    total += this.ref[ind].value
  }
  return total
}

This is totaly vaild in JS, should be in typescript too

[DanielRosenwasser]

You want number (all lowercase) not Number. number is the primitive type, whereas Number is a description of the shape of instances of Number and number itself.

See a more detailed response here: https://github.com/Microsoft/TypeScript/issues/2624#issuecomment-89914698

Or @danquirk's response here: https://github.com/Microsoft/TypeScript/issues/2031#issuecomment-74329927

[DanielRosenwasser]

Note that #2361 aims to address this.