How to check if two arrays are equal with JavaScript? [duplicate]

Answer 1

There is no easy way to do this. I needed this as well, but wanted a function that can take any two variables and test for equality. That includes non-object values, objects, arrays and any level of nesting.

In your question, you mention wanting to ignore the order of the values in an array. My solution doesn't inherently do that, but you can achieve it by sorting the arrays before comparing for equality

I also wanted the option of casting non-objects to strings so that [1,2]===["1",2]

Since my project uses UnderscoreJs, I decided to make it a mixin rather than a standalone function.

You can test it out on http://jsfiddle.net/nemesarial/T44W4/

Here is my mxin:

_.mixin({
  /**
  Tests for the equality of two variables
    valA: first variable
    valB: second variable
    stringifyStatics: cast non-objects to string so that "1"===1
  **/
  equal:function(valA,valB,stringifyStatics){
    stringifyStatics=!!stringifyStatics;

    //check for same type
    if(typeof(valA)!==typeof(valB)){
      if((_.isObject(valA) || _.isObject(valB))){
        return false;
      }
    }

    //test non-objects for equality
    if(!_.isObject(valA)){
      if(stringifyStatics){
        var valAs=''+valA;
        var valBs=''+valB;
        ret=(''+valA)===(''+valB);
      }else{
        ret=valA===valB;
      }
      return ret;
    }

    //test for length
    if(_.size(valA)!=_.size(valB)){
      return false;
    }

    //test for arrays first
    var isArr=_.isArray(valA);

    //test whether both are array or both object
    if(isArr!==_.isArray(valB)){
      return false;
    }

    var ret=true;
    if(isArr){
      //do test for arrays
      _.each(valA,function(val,idx,lst){
        if(!ret){return;}
        ret=ret && _.equal(val,valB[idx],stringifyStatics);
      });
    }else{
      //do test for objects
      _.each(valA,function(val,idx,lst){
        if(!ret){return;}

        //test for object member exists
        if(!_.has(valB,idx)){
          ret=false;
          return;
        }

        // test for member equality
        ret=ret && _.equal(val,valB[idx],stringifyStatics);
      });

    }
    return ret;
  }
});

This is how you use it:

_.equal([1,2,3],[1,2,"3"],true)

To demonstrate nesting, you can do this:

_.equal(
    ['a',{b:'b',c:[{'someId':1},2]},[1,2,3]],
    ['a',{b:'b',c:[{'someId':"1"},2]},["1",'2',3]]
,true);