en.javascript.info/1-js/2-first-steps/08-operators/3-primitive-conversions-questions/solution.md

"" + 1 + 0 = "10" // (1)
"" - 1 + 0 = -1 // (2)
true + false = 1
6 / "3" = 2
"2" * "3" = 6
4 + 5 + "px" = "9px"
"$" + 4 + 5 = "$45"
"4" - 2 = 2
"4px" - 2 = NaN
7 / 0 = Infinity
" -9\n" + 5 = " -9\n5"
" -9\n" - 5 = -14
null + 1 = 1 // (3)
undefined + 1 = NaN // (4)

1. The plus "+" operator in this case first converts 1 to a string: "" + 1 = "1", and then adds 0.
2. The minus "-" operator only works with numbers, it converts an empty string "" to zero immediately.
3. null becomes 0 after the numeric conversion.
4. undefined becomes NaN after the numeric conversion.