undefined true false px 4px null null null null undefined undefined 10

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undefined + ""
true + false
6 / "3"
4 + 5 + "px"
"$" + 4 + 5
"4px" - 2
null == "0"
+null == "0"
null >= 0
null > 0
undefined < 0
+undefined >= 0
x = y || 10;
x = y || (a = 7);
x = flag && 19;
x = flag ? 19 : x;
x = flag ? 19 : -1;
x = (a = 7), y, -1, (a = 8), 0;