limit strings length in pure javascript

string-limit.js

// add some prototypes
String.prototype.limit = function(length = 150, tail = '...') {
    return this.substr(0, length) + (this.length > length ? tail : '');
};

// how to use:
'this is an string'.limit(5);

// or it can be like the below
let name = 'this is my name';
alert( name.limit(10) );