javascript - Why can't '\b\w+(?=ing)\b' match "I'm singing while you're dancing" -


i have following regex

var reg = /\b\w+(?=ing)\b/g; var str = "i'm singing while you're dancing"; str.match(reg) // ==>null

but if regex /\b\w+(?=ing\b)/g str can match 'sing,danc'

why mach previous example doesn't?

you need remove \b @ end since part want match not end on boundary . danc , sing batch \b\w+\b dancing , singing not

\b\w+(?=ing)

check demo here 

\b\w+(?=ing\b)

would make sure ing @ boundary , not 

\w+

part


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