JSFiddle - React, Tailwind, and code Playground

JavaScript

var A = [
    "+-+ +--+  +--+",
    "| | |  |  |  |",
    "+-+ |  |  + -+",
    "    |  |      ",
    "    +--+  +-+ ",
    "  +--+    |   ",
    "  +--+    +-+ "
    ];

for(y=A.length,r=/\+-*\+/g;--y;)for(;m=r(A[y]);){for(w=m[0].length,z=y;A[--z][x=m.index]+A[z][x+w-1]=="||";);/^\+-*\+$/(A[z].substr(x,w))&&alert([x,z,w,y-z+1])}