ocomfd questions

• Why is Object.keys([,1,,1]) different from Object.keys([,1,undefined,1])?
• Why does the sum of float numbers with exact values still depend on order?
• For a positive integer n, is Math.random()*n >= n possible?
• Why is (function(){return this}).bind('abc')()==='abc' equals to false?
• How to eliminate if-else when doing different things according to different combinations of boolean value?
• Why is let=0 valid but not var=0? [duplicate]
• Why does 0.-5 evaluate to -5?

ocomfd answers