# JS

* **Handling empty array, null or undefined**

*Do's*
- Can use _.isEmpty, _.isNull

    if(!_.isEmpty(variable_name)){
        // do task
    }

*Don't*

    if(variable_name !== null){
        // do task
    }

* **Use lodash instead of JS inbuilt methods**

*Do's*
- Accessing object responsibly - to avoid uncertain behaviour

  let result = _.get(object, "firstChild.secondChild", defaultValue);

- Prefer filter over manual compare

  _.filter(array, item => {
      return !_.isNull(item);
  });

- Avoid repeated method calls - use it with time consuming methods or query

  _.debounce(func, time_before_accessible_again);

*Don't*
- Do not access objects directly

    let result = object.firstChild.secondChild || defaultValue;

- Do not use map for filtering

    _.map(array, item=>{
        if(item != null){
          return item;
        }
    })

* **Using map responsibly**

*Do's*
- Whole array traverse - map should not be used when you don't want whole array access

    for(let index = 0; index < max_length; ++i){
        if(array[index] == "desigred_value"){
            break;
        }
    }

*Don't*

     _.map(array, item =>{
         return item == "desigred_value";
     });

* **Cloning and comparing**
*Do's*
- cloning is required to remove value reference

    let clonedValue = _.cloneDeep(value);

- isEqual compares key and data, key order does not matter

    let areSimilar = _.isEqual(value, otherValue);

*Don't*

- Do not compare object by making strings, different key order will give false result

    let valueString = JSON.stringify(value);
    let otherValueString = JSON.stringify(otherValue);
    
    let areSimilar = _.isEqual(valueString, otherValueString);

We are using lodash for all JS standard methods, as lodash take care of undefined and all other edge cases. To learn more see [lodash documentations](https://lodash.com/docs).