This OLCC programming example page demonstrates getting information from PubChem E-Util using JavaScript.
This example gets the first 100 compounds with molecular weight between 149.9 and 150.1.

Press the "test" button to evaluate the JavaScript in the textarea below.
Feel free to modify the JavaScript and press test again.

// First we define to functions, pcGet and pcReturn. Notice that they call each other!
// pcGet calls pcReturn, which calls pcGet again. 
var pcGet = function(type, query, term, key) {
  // the term, if it is present must be URI-encoded. 
  term && (query += "&term="+encodeURIComponent(term));
  var url = "https://www.ncbi.nlm.nih.gov/entrez/eutils/" + type + ".fcgi?retmode=json&" + query;
  $("#url").html(url);
  $.ajax({
   url:url,
   dataType:"json",
   success: function(data){pcReturn(data, type, key)},
   error: function(data){alert("ohoh " + data);xxd = data;}
  });
}
var pcReturn = function(data, type, key) {
  switch (type) {
  case "esearch": 
    // The compound IDs are in data.esearchresult.idlist
    var list = data.esearchresult.idlist;
    $("#result").html(JSON.stringify(list,null,"\t"));
    alert("Shown below is the list of " + list.length + " returned PubChem compound IDs");
    var ids = list.join(",");
    pcGet("esummary", "db=pccompound&id="+ids, null, key);
    break;
  case "esummary":
    var info = data.result;
    $("#result").html(JSON.stringify(info,null,"\t"));
    var names = [];
    // we are looking for a specific key in data.result entries
    for (compound in info) { names.push(info[compound][key] || "??"); }
    alert(names.join("\n"));
    break;
  }
}
pcGet("esearch", "db=pccompound&retmax=100", "149.9:150.1[MolecularWeight]", "iupacname");

url:
result: