Javascript: replace all the literal or regexpr occurrences in a string

Replace FIRST occurrence only

“aaaaa”.replace(“a”, “b”) // baaaa

Replace ALL occurrences

“aaaaa”.replaceAll(“a”, “b”) // bbbbb

Advanced replaceAll using Rgexpr

Example with markdown, replacing titles with HTML tags

#this is the title
content

# another title
another content

to transform into

<h1>this is the title</h1>
content

<h1>another title</h1>
another content

This can be done with replaceAll taking all the content after a # symbol and spaces until the next line and outputting it inside h1 tags. Note that $1 means the content inside the first set of brackets.

stringAbove.replaceAll(/\n# *(.*) *\n/g, '\n<h1>$1</h1>\n')

Note also the usage of /g . this is necessary to include ALL the lines. Without that modifier, only the first line will be replaced.

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