selectCheckboxesの一括チェック処理サンプル

selectCheckboxes.page

<apex:page controller="selectCheckboxesCon" id="page">
    <apex:form id="form">
        <apex:selectCheckboxes value="{!countries}" id="checkBoxes">
            <apex:selectOptions value="{!items}"/>
        </apex:selectCheckboxes><br/>
        <apex:commandButton value="Apex Check!!" action="{!doApexCheck}" reRender="form" />
        <apex:commandButton value="JavaScript Check!!" onclick="return allChecked();" />
    </apex:form>
    <script type="text/javascript">
        function allChecked() {
            
            // apex:selectOptionsの件数を取得
            var itemCnt = '{!items.size}';
            console.log(itemCnt);
            
            // apex:selectCheckboxesのidを取得
            var checkId = '{!$Component.form.checkBoxes}';
            console.log(checkId);
            
            // リスト件数分チェック処理を実行
            for (var i = 0; i < itemCnt; i++) {
                    document.getElementById(checkId + ':' + i).checked = true;
            }
            
            return false;    
        }
    </script>
</apex:page>

selectCheckboxesCon.cls

public with sharing class selectCheckboxesCon {

    public List<String> countries {get; set;}
    public List<SelectOption> items {get; set;}
    
    public selectCheckboxesCon() {
        this.items = getItems();
        this.countries = new List<String>();
    }

    public List<SelectOption> getItems() {
        List<SelectOption> options = new List<SelectOption>();
        options.add(new SelectOption('US','US'));
        options.add(new SelectOption('CANADA','Canada'));
        options.add(new SelectOption('MEXICO','Mexico'));

        return options;
    }
    
    /**
     * ボタンクリック時にチェック
     */
    public void doApexCheck() {
        System.debug('Check = ' + this.countries);
        
        // selectCheckBoxsの値をセット
        this.countries = new List<String>();
        for (SelectOption o : this.items) {
            this.countries.add(o.getValue());
        }
        
        // selectCheckBoxsの値をクリア
        //this.countries = null;
    }
}