Why does adding a zero before a number change its value?

Question

Write out 074 in the console and it'll return 60.

074
>>60

Why?

Numbers with a leading zero are octal, just like numbers with leading `0x` are hex. — Niet the Dark Absol, Nov 15 '18 at 20:04
I agree with @Niet the Dark Absol... if you want to get 074 write into console "074" like a string... — Ferdinando, Nov 15 '18 at 20:08

score 5 · Accepted Answer · answered Nov 15 '18 at 20:05

Adding a zero before a number tells javascript to interpret it as an octal (base 8) value.

According to the MDN documentation on number literals, you can use the following to represent numbers on different base:

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