The issue with displaying line breaks in strings in Ext.MessageBox.alert() in ExtJs.

In the ExtJs Ext.MessageBox.alert() method, you can use \n to represent a line break. Example:

Ext.MessageBox.alert('提示', '这是第一行\n这是第二行');

Additionally, if you want to change the font style while breaking a line, you can use HTML tags to achieve this. For example:

Ext.MessageBox.alert('提示', '这是第一行<br><span style="color:red">这是第二行</span>');

The code above will insert red text between the first and second lines.