getMessage is not defined
<p>Why does this:</p>

<pre><code>function ConditionsTarifairesForm_required () { 
        this.a0 = new Array("dateDebutDeValiditeDuPlanDAffaires", getMessage('errors.required','Date de début'), new Function ("varName", "this.datePattern='yyyy/MM/dd';  return this[varName];"));
        this.a1 = new Array("dateFinDeValiditeDuPlanDAffaires", getMessage('errors.required','Date&amp;nbsp;de&amp;nbsp;fin'), new Function ("varName", "this.datePattern='yyyy/MM/dd';  return this[varName];"));
        this.a2 = new Array("tarifEnVigueur", getMessage('errors.required','Tarif en vigueur'), new Function ("varName", " return this[varName];"));
        this.a3 = new Array("dateDebutTarif", getMessage('errors.required','Date de début'), new Function ("varName", "this.datePattern='yyyy/MM/dd';  return this[varName];"));
        if(document.getElementsByName('delaiDePaiementFacture')[0].disabled == false) {
            this.a4 = new Array("delaiDePaiementFacture", getMessage('errors.required','Délai&amp;nbsp;de&amp;nbsp;paiement'), new Function ("varName", " return this[varName];"));
        }else {
            if(document.getElementsByName('delaiDePaiement.value')[0].selectedIndex == 7
            || document.getElementsByName('delaiDePaiement.value')[0].selectedIndex == 0) {
                this.a4 = new Array("delaiDePaiement", getMessage('errors.required','Délai&amp;nbsp;de&amp;nbsp;paiement'), new Function ("varName", " return this[varName];"));
            }
        }       
   } 
</code></pre>

<p>produce this error message: </p>

<blockquote>
  <p>Uncaught ReferenceError: getMessage is not defined</p>
</blockquote>