H5编辑器核心思想的实例分析

var range = getRangeObject();var start = range.startOffset,
end = range.endOffset;var startContainer = range.startContainer;var endContainer = range.endContainer;

function getRangeObject(){if(window.getSelection)
{var selection = window.getSelection();if(selection.rangeCount > 0)
{return selection.getRangeAt(0);
}
}else if(document.selection)
{return document.selection.createRange(); 
}return null;
};

function getNextTextNode(startNode,dir = "nextSibling"){//记录startNode变化之前的状态，startNode变化后无效时便于状态的回滚let unchangeNode = startNode;if(startNode.nodeType == 3){
 startNode = startNode[dir];
 }while (true){if(startNode == undefined){if(unchangeNode == undefined){//保护机制throw new Error("程序会陷入死循环");break;
 }/*startNode所在的父元素所有选中节点遍历完毕，将sartNode指向父元素的兄弟节点*/let parent = unchangeNode.parentElement;
 unchangeNode = parent;
 startNode = parent[dir];
 }else if(startNode.nodeType == 3){//文本节点则退出循环break;
 }else if(startNode.tagName == "BR"){//处理单标签,避免不必要的迭代unchangeNode = startNode;
 startNode = startNode[dir];
 }else if(startNode.nodeType == 1){/*如果是双标签元素则进入*/unchangeNode = startNode;if(dir == "previousSibling"){

 startNode = $(startNode).contents().last().get(0);
 }else if(dir == "nextSibling"){
 startNode = $(startNode).contents().first().get(0);
 }else {//便于错误的定位throw new Error("错误的遍历方向:"+dir);
 }
 }else {//便于错误的定位throw new Error("不期待的元素类型=》"+startNode);

 }
 } return startNode;
 
}

function getTextNodes(startTextNode,endTextNode){
 let textNodeArray = [];
 let node = startTextNode;while (true) {
 node = getNextTextNode(node);if(node == endTextNode){break;
 }
 textNodeArray.push(node);
 } return textNodeArray;
}