How can I easily concatenate typescript variable with string in html tag?

to make interpolation in the attribite of html element in angular you should use [attr.attrName]="expression" or in your case [attr.id]="'m' + elementid"

As explained in Angular documentation, you can use interpolation:

id="{{'m' + elementid}}"

or property binding:

[id]="'m' + elementid"

you can do this using square brackets,

   [attr.id]="m+'elementid'"