javascript - JS/TS/Angular2 - Replace characters while writing in Textbox -

i using ts/angular2 app. have textbox text of certain(important) length, , able control length, want replace next character 1 typed.

so, if i've got text "test" , courser position "t | est". if user types new character, want "e" replaced character.

so if type "a" @ position, result should "tast" instead of "test", if know mean.

i couldn't find (which might due disability find correct expression this). there way set "writingmode" or whatever it's called directly in code or have code manually?

thanks!