misc-math-symbols-fsm.js

var str = (function(expectedLength){
    var stateMap = {
        'empty': ['⦧', '⦦'],
        '⦧': ['⦦', '⦢'],
        '⦦': ['⦧', '⦢'],
        '⦢': ['⦣'],
        '⦣': ['⦧']
    };
    
    var random_ = function(arr){
        return arr[Math.floor(Math.random() * arr.length)]
    };
    
    return (function FSM(output){
        if (output.length === expectedLength){
            return output;
        } else {
            var state = output.charAt(output.length - 1) || 'empty';
            return FSM(output + random_(stateMap[state]));
        }
    })('');
})(140);

// Outputs something like: 
// ⦧⦦⦢⦣⦧⦢⦣⦧⦦⦧⦢⦣⦧⦦⦢⦣⦧⦢⦣⦧⦦⦢⦣⦧⦦⦧⦦⦧⦢⦣⦧⦦⦧⦦⦢⦣⦧⦦⦧⦢⦣⦧⦢⦣⦧⦦⦧⦢⦣⦧⦦⦧⦦⦧⦦⦧⦢⦣⦧⦢⦣⦧⦢⦣⦧⦢⦣⦧⦢⦣⦧⦢⦣⦧⦢⦣⦧⦦⦧⦦⦢⦣⦧⦢⦣⦧⦢⦣⦧⦢⦣⦧⦢⦣⦧⦦⦢⦣⦧⦢⦣⦧⦦⦧⦦⦢⦣⦧⦦⦢⦣⦧⦢⦣⦧⦢⦣⦧⦢⦣⦧⦦⦢⦣⦧⦦⦢⦣⦧⦦⦧⦢⦣⦧⦢⦣⦧⦢⦣⦧ 
console.log(str)