Mrthdrb

I am trying to make auto select first child product from the configurable product in product detail page.

Is this possible?

For Dropdown:

Override this file to your theme:

vendor/magento/module-configurable-product/view/frontend/web/js/configurable.js

your theme file location will be:

app/design/frontend/[vendor]/[theme]/Magento_ConfigurableProduct/web/js/configurable.js

Replace the _fillSelect method under configurable.js

_fillSelect: function (element) 
 var attributeId = element.id.replace(/[a-z]*/, ''),
 options = this._getAttributeOptions(attributeId),
 prevConfig,
 index = 1,
 allowedProducts,
 i,
 j;

 this._clearSelect(element);
 element.options[0] = new Option('', '');
 element.options[0].innerHTML = this.options.spConfig.chooseText;
 prevConfig = false;

 if (element.prevSetting) 
 prevConfig = element.prevSetting.options[element.prevSetting.selectedIndex];
 

 if (options) 
 for (i = 0; i < options.length; i++) 
 allowedProducts = [];
 if (prevConfig) 
 for (j = 0; j < options[i].products.length; j++) 
 // prevConfig.config can be undefined
 if (prevConfig.config &&
 prevConfig.config.allowedProducts &&
 prevConfig.config.allowedProducts.indexOf(options[i].products[j]) > -1) 
 allowedProducts.push(options[i].products[j]);
 
 
 else 
 allowedProducts = options[i].products.slice(0);
 

 if (allowedProducts.length > 0) 
 options[i].allowedProducts = allowedProducts;
 element.options[index] = new Option(this._getOptionLabel(options[i]), options[i].id);
 if (typeof options[i].price !== 'undefined') 
 element.options[index].setAttribute('price', options[i].prices);
 

 element.options[index].config = options[i];




 index++;
 
 // Code added to select option
 if (i == 0) 
 this.options.values[attributeId] = options[i].id;
 
 
 //Code added to check if configurations are set in url and resets them if needed 
 if (window.location.href.indexOf('#') !== -1) this._parseQueryParams(window.location.href.substr(window.location.href.indexOf('#') + 1));
 

,

For Swatch:
Override the below file to your theme

/module-swatches/view/frontend/web/js/SwatchRenderer.js

And update the method _RenderControls

_RenderControls: function () 
 var $widget = this,
 container = this.element,
 classes = this.options.classes,
 chooseText = this.options.jsonConfig.chooseText,
 selectedArray = []; // Variable declation for autoselect element array

 $widget.optionsMap = ;

 $.each(this.options.jsonConfig.attributes, function () 
 var item = this,
 controlLabelId = 'option-label-' + item.code + '-' + item.id,
 options = $widget._RenderSwatchOptions(item, controlLabelId),
 select = $widget._RenderSwatchSelect(item, chooseText),
 input = $widget._RenderFormInput(item),
 listLabel = '',
 label = '';

 // Show only swatch controls
 if ($widget.options.onlySwatches && !$widget.options.jsonSwatchConfig.hasOwnProperty(item.id)) 
 return;
 

 if ($widget.options.enableControlLabel) 
 label +=
 '<span id="' + controlLabelId + '" class="' + classes.attributeLabelClass + '">' +
 item.label +
 '</span>' +
 '<span class="' + classes.attributeSelectedOptionLabelClass + '"></span>';
 

 if ($widget.inProductList) 
 $widget.productForm.append(input);
 input = '';
 listLabel = 'aria-label="' + item.label + '"';
 else 
 listLabel = 'aria-labelledby="' + controlLabelId + '"';
 

 // Create new control
 container.append(
 '<div class="' + classes.attributeClass + ' ' + item.code + '" ' +
 'attribute-code="' + item.code + '" ' +
 'attribute-id="' + item.id + '">' +
 label +
 '<div aria-activedescendant="" ' +
 'tabindex="0" ' +
 'aria-invalid="false" ' +
 'aria-required="true" ' +
 'role="listbox" ' + listLabel +
 'class="' + classes.attributeOptionsWrapper + ' clearfix">' +
 options + select +
 '</div>' + input +
 '</div>'
 );

 $widget.optionsMap[item.id] = ;

 // Aggregate options array to hash (key => value)
 $.each(item.options, function () 
 if (this.products.length > 0) 
 $widget.optionsMap[item.id][this.id] = 
 price: parseInt(
 $widget.options.jsonConfig.optionPrices[this.products[0]].finalPrice.amount,
 10
 ),
 products: this.products
 ;
 
 );
 //Create array for Autoselect swatch
 selectedArray.push($widget.element.find('[attribute-id=' + item.id + '] .swatch-option')[0]);
 );


 // Connect Tooltip
 container
 .find('[option-type="1"], [option-type="2"], [option-type="0"], [option-type="3"]')
 .SwatchRendererTooltip();

 // Hide all elements below more button
 $('.' + classes.moreButton).nextAll().hide();

 // Handle events like click or change
 $widget._EventListener();

 // Rewind options
 $widget._Rewind(container);

 //Emulate click on all swatches from Request
 $widget._EmulateSelected($.parseQuery());
 $widget._EmulateSelected($widget._getSelectedAttributes());

 //Trigger click for Autoselect first option swatch
 $.each(selectedArray, function () 
 if(this != undefined) this.click();
 );

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