Issue with pushing values to a javascript array if it is a function

Question

I am trying to create a set of buttons that behave like a list, where an array is created from the values selected.

Below is the function for checking if the value already exists in the array, and if it does not it will not add the new value.

function linearSearch(arrayName, sValue) 
{               
    Array.prototype.exists = function(search){
      for (var i=0; i<this.length; i++)
        if (this[i] == search) return true;

      arrayName.push(sValue);
      return false;
    } 
}

Here is the jquery click function (of the listed items) where this function is called:

    con_array = [];
    $('.con_button').live('click', function (e) {
        e.stopPropagation()                              
        $(this).html('<div class="fun_button_center"></div>');
        con_value = $(this).attr('data-value');
        linearSearch(con_array, con_value);
        alert(con_array);
    });

The function works perfectly fine if it is inside of the click function without parameters. Yet in this circumstance, where it would be optimal because I can reuse it, no value is displayed with alert(con_array);

Victor Nicollet · Accepted Answer · 2011-06-28 07:18:00Z

1

At the very least, write your `linearSearch function this way:

function linearSearch(arrayName, sValue) 
{               
    Array.prototype.exists = function(search){
      for (var i=0; i<this.length; i++)
        if (this[i] == search) return true;
    };

    if (arrayName.exists(sValue) return true;

    arrayName.push(sValue);
    return false;     
}

It's brittle to monkey-patch Array this way, though, so you can either monkey-patch it at global scope (still ugly, but at least it's both faster and available everywhere:

Array.prototype.exists = function(search){
  for (var i=0; i<this.length; i++)
    if (this[i] == search) return true;
};

function linearSearch(arrayName, sValue) 
{    
    if (arrayName.exists(sValue) return true;

    arrayName.push(sValue);
    return false;     
}

Or you can just inline that loop:

function linearSearch(arrayName, sValue) 
{    
    for (var i=0; i<arrayName.length; i++)
      if (arrayName[i] == sValue) return true;

    arrayName.push(sValue);
    return false;     
}

answered Jun 28, 2011 at 7:18

Victor Nicollet

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3 Comments

Alnitak Over a year ago

ES5 has Array.prototype.indexOf() - no need for an exists function.

TaylorMac Over a year ago

Thank you for then many options. I will go for the simplest without using a prototype, the array contains no more than 5 values. Thank you

Victor Nicollet Over a year ago

@Alnitak: stackoverflow.com/questions/3629183/…

YODA · Accepted Answer · 2011-06-28 07:28:17Z

0

You can try like this:

Array.prototype.exists = function(search){
      for (var i=0; i<this.length; i++)
        if (this[i] == search) return true;

      this.push(search);
      return true;
} 

function linearSearch(arrayName, sValue) 
{               
    arrayName.exists(sValue);
}

answered Jun 28, 2011 at 7:28

YODA

3091 silver badge3 bronze badges

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