How to replace substring in Javascript?

replace only replace the first occurrence of the substring.

Use replaceAll to replace all the occurrence.

var str='------check';

str.replaceAll('-','');

simplest:

str = str.replace(/-/g, ""); 

str.replace(/\-/g, '');

The regex g flag is global.

Try this instead:

str = str.replace(/-/g, '');

.replace() does not modify the original string, but returns the modified version.
With the g at the end of /-/g all occurences are replaced.