I have a string something like this
Material TD Vandal High Supreme Signal Blue / University Red-B
I want to add hyphen, so final string becomes
Material TD Vandal High Supreme Signal - Blue / University Red-B
Hyphen should be added word before first /
string can have multiple /
i tried string.replace(/([A-Za-z][ ][/])/g, '-$1');
tried few more things, but nothing is working.
When you say Hyphen should be added word before first /, the question is why did you use /g modifier? g means "global", it will try to find all non-overlapping occurrences of the regex match in the string. You do not need that modifier in the first place.
Second, [A-Za-z] matches a single char. Since the regex engine matches strings from left to right, the letter that is matched with this pattern should be followed with a space and then a slash, hence, it will match e /, not Blue /. To match a whole word, you will need to add a + quantifier after [A-Za-z]. You might also just use \w if you do not care if those are letters or digits (or _). Even \S+, one or more non-whitespaces will work.
To keep it close to the original, I suggest:
var result = string.replace(/[A-Za-z]+\s+\//, "- $&");
See the regex demo.
Details
[A-Za-z]+ - 1 or more ASCII letters\s+ - 1+ whitespaces\/ - a / char (escaped because it is used in a regex literal).The $& in the replacement pattern is the replacement backreference that refers to the whole match, no need wrapping the whole pattern with a capturing group.
.replace(/[A-Za-z]+\s+\//, "- $&"), see this regex demo