JavaScript method to control font size setting

When making the company's official website, the news page will have a function that allows viewers to adjust the text size themselves, so in this free time, I sorted out this function:

function setFontSize (id,content,params){
      var oTarget = document.getElementById(id),
        content = document.getElementById(content),
        size = params.size || 14,
        maxSize = params.maxSize || 20,
        step = params.step || 2;
        oBtn = &#39;<input type="button" value="+"/><input type="button" value="-" />&#39;;
        oBtn1 = null,
        oBtn2 = null;
 
        oTarget.innerHTML = oBtn;
        oBtn1 = oTarget.childNodes[0];
        oBtn2 = oTarget.childNodes[1];
 
        oBtn1.onclick=function(){
          if(size+step <= maxSize){
            size+=step;
          }else{
            size = maxSize;
            this.className+=&#39; disabled&#39;;
            this.disabled = true;
          }
          oBtn2.className.replace(&#39;disabled&#39;,&#39;&#39;);
          oBtn2.disabled = false;
          content.style.fontSize = size +&#39;px&#39;;
        }
        oBtn2.onclick=function(){
          if(size-step >= 12){
            size-=step;
          }else{
            size = 12;
            this.className+=&#39; disabled&#39;
            this.disabled = true;
          }
          oBtn1.className.replace(&#39;disabled&#39;,&#39;&#39;);
          oBtn1.disabled = false;
          content.style.fontSize = size +&#39;px&#39;;
      }
  }

Call method:

setFontSize(id,contentid,{size:,maxSize,step:});
/*
 * id ：用于存放增加或减小两个按钮的父级盒子的id。
 * contentid: 存放内容的id。
 * {} 一个对象，用于提供设置的参数。
     |— szie : 字体起始(默认)大小。
     |— maxSize : 最大字体。
     |— step : 增长的步长值。
*/

Tips: You can hide the value of the Input element through font-size:0, and then customize the button style.