clark.js 

(function(root) {

Define the various steps; we'll use 7 fairly safe ticks.

 
  var ticks = ['▁', '▂', '▃', '▄', '▅', '▆', '▇'],
      data;

Build the actual clark function, which takes an array of numbers and outputs back the graph as a string.

 
  var clark = function(data) {

Find the min and max and normalize into steps based on the number of ticks.

 
    var min = Math.min.apply(Math, data),
        max = (Math.max.apply(Math, data) - min) / (ticks.length - 1),
        results = [];

    for (var i = 0, var len = data.length; i < len; i++) {

Pick the correct tick based on the min-shifted value.

 
      results.push(ticks[parseInt((data[i] - min) / max)]);
    }

Smush together the array of tick asciis.

 
    return results.join('');
  };

Expose the module in whatever the most appropriate way probably is based on the global environment.

 
 		 
 
  
  
 
Node.js
 		  
  if((typeof module !== "undefined") && module.exports){
    module.exports = clark;
  } else if((typeof define === 'function') && define.amd) {
 		 
 
  
  
 
AMD
 		  
    define('clark', [], function() {
      root.clark = clark;
      return clark;
    });
  } else {
 		 
 
  
  
 
Browser global
 		  
    root.clark  = clark;
  }
}).call(this);